This is not quite what you asked, but I think compressing the late-game tech tree affected gameplay for the worse. I can't say exactly how, since I've barely played the base game. It's not that I think a large number of turns is needed per se, but I think something about the pacing and order of events is awkward. One clear issue (I think I did mention this one before) is that there are buildings that are not worth building, since they'll get so little use. Once you compress the late eras like that that, you really need to redesign ~all~ of the gameplay elements so that they work well in the context of a smaller number of turns. But I don't think you need to compress it at all. I think you might as well leave it the way it was originally, except for the mecha and whatever other tweaks you need. With the emphasis on RP victories, most games are not going to play for that long anyway, so it doesn't matter if the total possible number of turns is large. It doesn't hurt.