Wodan:
No problem. This is a great way to discover strategies and specific moves, and I don't mind waiting.
In the literal sense of "require", you're correct. However, the Rifling beeline has at least 3 optional paths, one of which goes through Civil Service.
If you really wanted, you could go through Guilds instead, or ... I don't remember the other one. In any event, I'd say you definitely should go through either Guilds or Civil Service. Not having either Knights or Macemen would be too much of a handicap. And, since Macemen upgrade to Riflemen and pass on CR promotions, it would seem a more obvious choice.
The Rifling beeline requires Gunpowder, which requires either Education or Guilds. If you're going through Education, you'll need either Theology or Civil Service. In terms of research cost, going through Civil Service is probably the most expensive route, since it requires both Education and Civil Service, both expensive techs compared to their alternatives.
Moreover, if you're going to go for a "beeline" to Rifling, it makes no sense to get the Liberalism line of techs because you're going to need Guilds for Banking anyway, so going that route saves you nothing and adds all kinds of unnecessary techs to your "beeline." You'll need Paper, which you can gain from Theology (cheaper than Civil Service), but not Civil Service nor Education.
It's "possible" to get Civil Service, but in terms of a Rifling beeline, you have no need for it at all. It's not another "optional" line, because it doesn't save you from getting Guilds at all. It is absolutely a detour.
Now, if you're going to go through Education to get to Gunpowder (which is unnecessary because you're going to need Guilds sooner or later, making Education wholly unnecessary) then you might as well go for Liberalism and race for it. If you get Liberalism, then you also get Gunpowder (or whatever) for free and it doesn't cost you anything.
It's not a beeline in any reasonable sense if you at all opt for Civil Service.
In contrast, going for Military Tradition
does require Civil Service because you need it to get Nationalism, which is opened with Civil Service and Divine Right or Philosophy.
It is more true that a Military Tradition liner is going to have Macemen and Civil Service than it is for a Rifling liner. Of course, if we're going to have the Rifle beeliner go for the Liberalism techs because they're just that valuable, then we might as well assume a similar setup for the Military Tradition liner and we devolve to a post-Liberalism scenario, exactly as I assumed was reasonable.
If we're to consider tech costs that far back, then the Military Tradition lines gain even more speed, because he doesn't need either Banking or Guilds whether or not he takes the Liberalism line of techs, whereas the Rifling liner needs to take Banking and Guilds whatever he decides to do.
If you truly wish to assume a lost or given up race (not even going for Liberalism), then the Military Tradition line is
much faster, for all that Nationalism is a horrendously expensive tech (which is normally offset by Liberalism's free tech). Once you gain Civil Service (and switch to Bureaucracy) you can almost always go direct to Nationalism, since Philosophy is a cheap Classical Age tech - easily acquired. Music is only 600 beakers, then Mil Trad only 1800. It's quite possible to acquire Cuirassers while everyone else is just beginning their Medieval tech wars. I know because I've done it - acquired Cuirassers before I even acquired Knights.
I can tell you that getting Cuirassers that early is a strong advantage. Not as strong as a Cavalry Rush was before, but I'm sure you can appreciate now how absurdly unfair that was, given the relative beaker costs of beelining.
You'll still need to get Gunpowder (Guilds or Education) before Grenadiers, but that's relatively a more relaxed race, since you already have the military advantages of Bureaucracy or Nationhood, and Cuirassers with which to win your wars. Of course, if you manage to build Taj Mahal, it'll go all that much quicker. If you go for Guilds, it's much faster than going through Paper-Education. You can assemble a Drafted Musketmen/Cuirasser army quite fast.
Always assuming, of course, that Liberalism was never in contention.
Given "judicious use of Cannon or Artillery," you can use just about anything against anything with some success.
Not "excessive." "Judicious," meaning even moderate. An Infantry has a Strength of 20 against a Cavalry's 15. The odds are somewhat against the Cavalry, but it can still win on quite good odds provided it has the Pinch promotion and the Infantry is damaged somewhat, say half hitpoints.
Compared to odds against a Riflman, it's not that far off. A Rifleman has only 14 Strength, but is +25% against Cavalry (since it's a mounted unit), so it's almost as good as Infantry against Cavalry. From experience only, without looking at the numbers, I'd say that there's almost no difference between the resistance of Infantry and Riflemen against Cavalry.
Since I can and have used Cavalry against Riflemen, I also have good results with them against Infantry. Seriously.
OR4NG3:
Also requires Airships and assumes that Infantry are not promoted and for some reason have no siege of their own to help them and are too afraid to attack the stacks of strengthwise inferior units that can all be beaten 1v1, considering that none of them get defensive bonuses. So yeah you're right..... :-/ I think cavalry should have its age extended and should be more of a threat to infantry rather than just the siege units.
Actually, you only need Cannon or Artillery and Infantry of your own. You can't hope to match Riflemen against Infantry. The weakness of a Rifleman/Cavalry/Cannon stack against Infantry is totally because Riflemen wilt against Infantry. With an Infantry/Cavalry/Cannon stack, you'll do quite well, in many respects much better than with just an Infantry/Cannon stack.
For one thing, you can annihilate entire stacks of enemy Cannon with your Cavalry.
Yes Assembly Line is some way away from riflery but it is closer to a "rifling techer" than it is to a "grenadier techer". Obviously it is situational but if you manage to crush one of your neighbours with riflemen you will soon be ready for yet another "superior unit war" with Infantry against your other neighbour. Oh and you get to upgrade all of your highly promoted riflemen.
Actually, the correct unit to counter Infantry with if you don't have Infantry is Cavalry. Shocking, I know. Your Grenadiers and Riflemen won't stand a chance, so don't even try. Cavalry stand a much better chance of killing Infantry than either of those units. Therefore, you can't really "counter" a Cavalry user with Infantry. He's already got the tech and units to more or less deal with the problem within his borders.
I agree, but I was imagining a simpler scenario where 2 players have the same techs but one wins the race to liberalism. Obviously one of the players is a "riflemen techer" and the other is a "grenadier techer". What would happen if the "riflemen techer" won? I'm sure it would be as I described: the grenadier techer would be missing 2-3 cities by the time he gets grenadiers, so pretty much the same scenario as if the "grenadier techer" had won, but vice versa.
Such is the power of free tech.
I do agree with you though that the Cuirassier+Grenadier scenario provides a smoother military transition, without weak points and with possible constant domination: 1st with cuirassiers then with the help of grenadiers and finally with the help of cavalry and cannons. However this comes at a cost of longer wars with more units involved, which essentially could slow down player's research.
Nope. Wrong there. The wars don't last longer. The military power scaling swings up longer, but the wars don't necessarily follow. It's a failsafe, not a requirement.
I'm telling it from the perspective of someone who's done both, and with various Civs. You can use Cuirassers with stacks of siege and "normal" units. In that function, they're every bit as devastating as Riflemen. Slightly cheaper, they're also slightly faster, in that the entire Cuirasser stack can move into a city in the same turn that they attack its defenders.
If you're only going against a couple Longbows or Crossbows plus maybe one Pikeman, Cuirassers can be almost as fast and deadly as Cavalry. They won't have the culture-punching power, so you'll need to neutralize defenses with Spies, but with that caveat, you can just overrun lots of cities with pure Cuirasser stacks.
The threatened future presence of the Grenadiers is only insurance against any untoward incident. You don't need them, strictly speaking, to wage an effective war. You'll do well enough with Cuirassers/Musketmen/Trebs on Nationalism or Bureaucracy.
If that's still not enough, Cannon is only one tech away from Grenadiers.
The fact that the military power of the tech up continually escalates is not an indication that it's only effective when you do so, and that you're going to need all that time to win your war. At any time you feel you've won the wars you want, you can simply get off the tech track and pursue more peaceful technologies.
I agree with almost everything you said. 
Given "judicious use of Cannon or Artillery," you can use just about anything against anything with some success. 
