elprofesor
Pluri-editing poster
You have not yet answered to my question. If that is such a big part to the game, then why Firaxis denied this “big part of the game” from at least two civs, England and Rome? That just does not make any sense.
Ok, let's see if we are on the same page here: your main concern is that some civs have UUs that give benefits to later upgrades, while some civs don't, and you feel that this is unfair. Your argument is that, since not ALL civs have a UU with a benefit that carries over, it must be a mistake from Firaxis. Correct me if I'm wrong.
And I believe that most civs that don't have a carry-over UU have more significant boni that do last less time, and that this is usually enough to balance them.
You argue against me that the fact that they have a bigger boost is irrelevant, since to make use of it you have to be at war just as you unlock said UU, while for carry-over UUs, you can be at war any time afterwards.
My personal opinion is that, when you have a non-carry-over UU, you have to plan around it, so that you are indeed at war as you finish the beeline towards your UU, which most of the time is possible and very beneficial, even moreso since you will end up with extra cities and a highly promoted army for future invasions. The extra survivability and promotions of your army might even make up for the absent special promotions.
The only reason that would forbid to do this is if the UU comes very early, and you are isolated (small continents, for example). That sucks, but at least you don't have to spend hammers and money on an army for a long time, and you can beeline scientific techs safely.
Note: I am not against giving extra promotions to all UUs. What I'm trying to convey is that I believe it's not really necessary, and that the game is already quite balanced for most civs (there are exceptions, but the only one mentioned in this thread is England, whose only Unique Characteristic for 99% of the games is the Longbowmen, since Naval warfare is irrelevant). Plus, you get more diversity this way (in my opinion, which apparently differs from yours).
And there is a pretty big difference between having an "upgradable" extra promotion, and giving all your units that extra promotion. The first one requires a heavy investment early on (when you could have been building and buying more important things), and it disappears as the game goes on.