Two things I'd fix in tech systems if I were making a strategy game are the lack of variation of availablity and not representing the needs for both initiative and failure in order for technology to progress.
China's economy today is an excellent example of the variation problem. They have access to modern technology and methods and use some very modern techniques in some areas (typically coastal) but in more backwards geographic areas, things can look much as they did 100 years ago. Because researching a technology doesn't mean it helps you everywhere, the technology has to be adopted locally to affect things locally. There is the "upgrading" of old equipment which some games model, but that's hardly the whole story. There has to be an incentive in place for the technique to spread, there local region needs to be important enough for the technique to be adopted and the economy has to reject the old technique, which can be a very traumatic process that meets much resistance. A technique might have no upgrade cost in equipment but can still take a very long time to spread.
Initiative and failure is problematic because it get's into meta-gaming. The players already know the value of the techs, so they can make descisions that no one would make at the time. Or even if these descisions were made, they'd be met with institutional resistance. Look at tanks in WWI for example. England, France, Germany and America all had the technical ability to build tanks in 1914. By 1918, it was obvious to all these nations that tanks were a weapon of great potential and they sure wish they'd been pursuing them in 1914 or before. But before the war both the Austrians and British rejected tank proposals because the merits were far from apparent at the time. A game might model these as needing to research prequisites (engines or something) first or setting date you have to wait for, but neither of these would reflect the system very well. What really is needed is first for the opportunity to arise in which an idea can be attempt then second for someone with initiative to dedicate his ability to getting that idea accepted, rather then another. Merely giving a budget towards new techniques, doesn't get them sought.
The other part to this of course is that failure is an essential part of the creative process. Keeping in the WWI era, look at the Wright Brothers and the airplane. No mater how good their design was, it had to fail the first time before they could build a successful aircraft. That was because they were using flawed air tables. They needed new air tables, but until they're first plane failed, they had no way of knowing they needed new air tables. Being good or having more resources helps you spot what you need to do faster, but an indispensible part of learning is taking the time to try and fail an attempt.
Or sometimes entire avenues can be failures but be needed to research anyway. Look at hydrogen fuel cells, a completely futile avenue as the energy density for hydrogen is simply too low and nothing will change that. We're pissing away billions on that technology, but that's to be expected. You have to try out the dumb idea's before you can know they're dumb. It's unlike that we'd be willing to try electric cars for example if we wouldn't give hydrogen funding. The only thing really surprising is that we're still pissing the money away after realizing how dumb this tech is but hey, that's the institutional resistance thing again. Initiative and vision in your research organizations can help you direct more of your efforts towards more worthwhile avenues but failed efforts are still a big part. Even Einstein got sidetracked into trying to trying to come up with a unified theory on his terms, something that it seems likely can't be done. On the other hand, once you know what's a good idea, for instance, if someone has done it before, you have fewer failed avenues to explore, even if you don't know exactly how it's done.
So yeah, what I'd like to see is a game that represents how the factors affect us coming up with workable idea's an implementing them. Future technology doesn't have to be unknown, but only let the player give general guidance to what to pursue rather then picking the exact tech for their needs. But offer the chance to focus efforts back if your facing a situation where an undiscovered tech's utility is apparent. Facing tanks tells you need to try anti-tank weapons, letting you focus on those rather then broader technology. It doesn't let you pick a bazooka or anti-tank cannon however, as your researchers don't know how effective those would be yet. But it would say that tanks are clearly very effective and allow you to focus on the technology the tank displayed. These focuses are the better results possible since institutional resistances are possible. Maybe you could even have a reserve of inspiration points or characters capable of focusing on the worthwhile idea's in one area due to grasping the implications of a technology. But the more narrowly you focus on something the more it hurts general technical research since that talent is missing elsewhere. Factor in failed attempts, you need to make failed prototypes and that means having the capacity that the tech needs to be used. Then finally add in the incentives that create the opportunity for a technology to be pursued, like how the desperation of WWII caused so many technologies to be attempted, some failures some not. Yes, funding research is a part of this, but it's also why anyone is interested in a research avenue in the first place. For instance Isreal is very paranoid about it's soldiers lives, so they have the best protective technologies in the world. A game could model this by making a player that accepts the limitations of being a "free" society would be able to pursue more protective technology idea's if under constant attack, translating to more successes. Or maybe one faction is preset to have this concern and would get that bonus, either way, it would give flavor.
So yeah, I think a system that had factors like this would be much more unpredicable, adding more strategy and have a lot more flavor then a system where you buy techs, like any system I've seen right now.