I’d want tech trees to be more varied, more complex, and a far greater number of things to research. (Somewhat akin to Civilization in terms of number of techs… or at least how long you’re researching new techs, relatively speaking.)
This would translate to me as a game with ‘more depth’. I don’t, necessarily, like in AoE2 having every single tech researched every game shortly after Imperial Age. I’d more want it to be that if the game really drags on for 2 or 3 hours, you still haven’t researched everything there is, and there are still some neat, nuanced techs yet to research.
I’m not a big fan of an apocalypse technology being researchable shortly into the final age; whereby whomever researches it first yields cataclysmic powers over their enemies and the game comes to a quick end. Or a tech that provides such an awesome economic boost that others get left in the dust right away. I think AoE3 had something along these lines, if I’m not mistaken.
Such apocalyptic techs or economy boosts could come eventually, sure… but more like an hour+ after hitting the final age… after you’ve continued to research cool stuff for that hour spent in the final age. Something like this, rather than having everything pretty much researched 5 minutes after hitting the final age.
And each civ being uniquely different, to a reasonable extent (i.e., as much as possible). It’d be a lot of development work, no doubt, but at least for Single Player or games with friends, it’d be nice. Especially if the save game function works where you can resume them at a later date, particularly after a patch update, and 10 years from now, too.
For ranked games, I could see this as not too desirable, because everyone only wants to play for about 30 minutes, probably.