Most 4X games I've seen over the past decade have been using the mainstream Research system (a system I've even seen employed in various other games, such as XCOM to state a contemporary title).
In essence, the system gives you resources (research points) that are a measure of time invested towards achieving a discovery in a given field.
In many 4X games, you have control over this resource by building variants of a research complex / science building of some sorts.
There are two side-effects of this system I'd like to discuss here:
1 - This creates a time reference where a game turn appears "longer" and "slower-paced"
The concept itself hints that you're actually doing the research in fields never before experimented with. Researches take time, and discoveries take even more. From the player's standpoint, if 5 game turns yield you a major discovery, you'd be tempted to count these turns in matter of months or years, and the overall relative time flow of the game will be affected.
2 - It becomes a "must" as it increases exponentially your army's efficiency, and it becomes impossible to achieve victory with sub-par technology
Let's face it, most 4X games are won by technology. Efficient ship design will not matter, not matter how well you can concentrate your force, if your opponent's science is two notches ahead of you. And it's extremely hard for developers to balance technology in a way there there aren't necessarily bad choices.
In most games I've played, investing in economy, in an effort to bring numbers, was always much weaker than investing in tech and have the next-gen shield/laser.
It's not necessarily a bad thing, as a tech-race might be fun gameplay too (especially given the choices) but it generally gets old, especially after playing yout 101st 4X game in a row.
Therefore, I'd like to discuss an embryo of a suggestion I believe might work better, which assesses both of the previous side-effects.
The concept, in and of itself, is that rather than having the player perform the research of new technologies, they'd rather need to fit their infrastructures in order to support existing (but hardly mainstream) technologies.
This system supposes that Beams/Shields techs 1-10 already exist and are established facts amongst the scientific populace, but have yet to be used outside of their testing labs.
As a result, rather than invest in scientists and their labs to come up with proof of concept, all you need to do is retrofit your starbase with the necessary tools/components/resources to build such gear.
Each "technological advancement" is a sizeable investment you need to make in terms of resources, and just because one of your starbases has acquired the capability to produce tech 7 beams doesn't mean the others do.
This creates a form of localized investment which is repeatable and requires consideration.
It assesses # 1 in that it would be possible to think of a game turn as 1 day or 1 week, given that the tech already exists and only requires you to burn overtime hours in setting up your infrastructures to build it.
It assessed # 2 in that it hardly scales. While its quite possible that one of your starbase quickly becomes maxed out with high-tier components, it doesn't help you defend the outskirts as your built ships will require you to move the extra distance. Likewise, if you want several starbases to be maxed out, you'll be spending a hefty count of resources to keep them up to speed, and that will mean that much less ships in your fleet.
It also comes with a finite endpoint (say 10) so that it avoids power creeping past the initial state of investments.
More importantly, it can factor local resources and whatnot, in such a way that you can only produce level 10 beams from a specific starbase in your empire, which is nowhere near your level 10 shield starbase. Assembly requires you to ferry parts aboard large freighters and find a suitable starbase to assemble the actual ships.
I've been tinkering with such a system and I'm trying to find the potential pros/cons I may not have discovered so far.