Let´s face it.
In the end Civilization is about a COMPETITION between different civs, there´s everything is about technology and resources, whoever gets first to the space age and builds a spaceship wins, it´s different races at different times, race to get to gunpowder era, race to get to the space age etc. and after the space age has begun its a building race, who builds a spaceship fastest wins, that´s the easiest way to victory in my opinion, just curl up defensively and build your spaceship and wait for a few turns to win.
I think the space race should be made a whole lot more difficult, it´s not just that you can build a starship like that, you would need technology far beyound our current tech level to accomplish that, like faster than light drives or cryogenic freezing and wakening technology plus a whole lot of other technologies to make it even remotely possible.
Colonization of Mars would be a first step to the stars, first build bases to the Moon and Mars and space stations to support permanent living in space and THEN you can start dreaming about going to the stars and even one starship would not bring final victory but you would need several (the amount of starships needed could of course be modded, if you want it to end in one starship just make it so by modding it), that´s my opinion about the space race victory, it´s TOO EASY.
Usually I turn the whole space race off, not to allow any civilization the easy way out, FIRST you have to UNIFY the world under one banner the easy way (diplomatic) or the hard way (war), personally I prefer diplomatic victory, it is the most peaceful and harmonic way to end the game and anyway, even going to Mars is going to be a global effort, the ISS already is, the space race is too expensive for any nation alone, not even the mighty U.S. can shoulder the costs alone, the moon program is already in danger when the economy took a hit in the latest financial crisis, will we see a man on the moon in 2020 like they promised or will the U.S. run out of cash?
Anyway, it´s not likely that we´ll have a fleet of starships like in Battlestar Galactica by 2050 or even one like in Civilization.
As for combat values, I mentioned that you can do quite a many tricks with just one combat value that you then alter by modifiers, that could work quite well and it´s not too hard to learn or memorize.
Why would you even need to memorize any of those values, just common sense and a little bit of history knowledge would do the same thing if the system is REALISTIC, you don´t attack riflemen or spearmen with cavalry, not to mention machineguns, history has a few lessons on that. The English cavalry had a tough time at the battle of Stirling bridge in Scotland against Scottish spearmen, anyone seen Braveheart? And in the beginning of WW-1 british cavalry was ordered to charge against advancing Germans to try to delay them, the Germans had machineguns with them and the rest can be guessed, the cavalry was turned into cheap salami (horse meat sausages

)and the Germans kept advancing.
That is simply why realism is a good thing, it makes those COMMON SENSE things real, despite their bravery Zulu spearmen had no chance against British rifles at Rorke´s Drift, despite the British force being only about a company strong or 100 men or so and the Zulus numbering in the thousands, it was completely catastrophic for the Zulus, they lost a major part of their army just by attacking a single company of only 100 men or less.
Since civilization is a game of competition, wars are inevitable at the very least they will result in the endgame, when someone launches a spaceship and everyone tries to capture their capital before the ship reaches Alpha Centauri (Are there even suitable planets at Alpha Centauri? That could be a part of the space race too, the search for suitable planets.)
I for one would prefer the wars to be REALISTIC when they happen, which is unfortunate, I usually prefer to maintain a peaceful world, but that will simply be boring, you NEED some amount of carnage to make the game FUN, correct?
REALISTICALLY, war is not fun, dead bodies are not fun, nuking a city is not fun, burning people and children alive with napalm or nukes is not fun.
In Sid Meier´s Alpha Centauri if anyone remembers a game of that name, nukes were an ATROCITY, anyone nuking anyone would get the whole world declaring permanent war of extermination on them, anyone using nukes was to be exterminated from the planet by the rest of the factions. I say bring that back, no economic sanctions or diplomatic minuses, just exterminate the hapless civilisation that uses a nuke.
If you decide you want to nuke someone, be prepared to nuke all the rest of them aswell, because after that, your only option is a complete conquest victory, the complete extermination of all rival civilisations, that should bring about lots of fun.
The question I think needs to be asked is, WHAT IS THE OBJECTIVE OF THE WAR SIMULATION?
Is it to be REALISTIC?
Or is it to be FUN?
Or BOTH? (Can a war simulation be both realistic and fun?)
If you want a FUN war simulation, then Red Alert is a game for you, it´s a tongue-in cheek simulation of war, you build buildings and troops and then you run them over with a tank, lot´s of fun.
The question is, WHAT MAKES WAR FUN? WHAT IS THE ELEMENT THAT MAKES THE WAR SIMULATION FUN?
In my opinion REALISM is exactly what makes it fun, not the guts and blood, but the fact that there are so many things to consider, so many variables.
You can simulate a lot of different aspects with just ONE number, with modifiers, so one number for both attack and defence will do if its well done, you just use modifiers like -50% WHEN DEFENDING or -50% WHEN ATTACKING to simulate different things.
Additional values could and should be used to simulate the combat environment more realistically.
Like MORALE, this would be the fighting spirit of the unit, if a unit has 120% morale it does extra damage and so on the soldiers are really pumped up and ready to fight. On the other hand if morale drops to 0% then the unit withdraws or more likely flees in panic or maybe surrenders.
You can have units which do primarily "morale damage", psychological warfare units which terrorize the enemy and lowers their morale etc.
DISCIPLINE has been used in Paradox´s strategy games as a value, it can be a modifier to MORALE, more disciplined troops lose morale slower and stay in the fight longer and are less likely to run away than ordinary peasants with pitchforks.
ORGANIZATION has also been used as a value. When a unit begins combat it has 100% organization, it is in good formation and well organized, when a battle progresses and especially in melee combat, the unit loses coherence and the formation starts to disintegrate into chaos, in the end who ever has more organization wins, like the Roman legions, they were so effective because they had good ORGANIZATION and stayed in formation better than barbarians, in ordinary combat one-on-one the Roman soldier might not be any better than the barbarian and without the help of his comrades the winner would be the one with more SKILL with the sword, there´s another value SKILL, how skilled are the units men with the sword or with the rifle, more skilled units win more fights and shoot more accurately doing more damage. Completely REALISTIC and if you like to have lots of variables to consider, then it is FUN aswell.
And yes the system can be made to simulate ALL weapons from clubs to handguns, from arrows to stealth bombers etc.
That´s one fun thing about civilization, it simulates the whole of history, why not simulate it as REALISTICALLY as possible, I say it´s more fun that way.
So, I say ONE value for attack and defence with modifiers if it is well done will do, PLUS more values to simulate combat more realistically, values like SKILL, MORALE, ORGANIZATION, DISCIPLINE, LOYALTY (disloyal troops can defect to the opposing side at the beginning of war or if you run out of cash)
In addition DESERTION and DISEASE could be made part of the game, units lose men to disease and desertion when in enemy territory.
FLANKING ATTACKS should be made part of the system aswell, if a unit is facing north and it is attacked from the east or the west or worse from the south, then the unit is most likely massacred unless it has a tactic like the infantry square to help them, just a matter of HOW you simulate it.
AND the fact that you have multiple values does NOT make it any harder, you don´t need to MEMORIZE all of the values, just some basic common sense rules, don´t attack machineguns or similar units with cavalry etc.
Cheers!