5 isn't too many. You can reach that pretty fast with the standard starting resources. I haven't done much testing yet though. One balance issue is that come civs have houses worth more pop that others though.
Needing 5 buildings make them a bit more balanced because the hose type with the lower pop cap/wood ratio (bad/less efficient) is cheaper per house and so the needed structures can be reached faster (with less wood) with such civilizations.
Iberians start with walls and towers by default (which are city phase buildings) but they don't start in city phase (which I think is good. The walls seam already hard to balance for me).
For me most things are not considered "logical" in RTS games so having the goal of being "historically accurate" for me applies mainly to the text and the story told in a game. I could wright a list of 100 items right know that are unrealistic but it's not the question for me. It's a game and it should be fun and on the one hand complex enough to stay interesting for a long time on the other hand not too complex that you can't catch up with what you want to do in theory while the game runs in realtime. So both, realism and historical correctness, don't count for me when it comes to gameplay issues. Those should be clearly separated! Art, text, story and others would be good if historically accurate and realistic (as long noone feels offended by this, well, or at least not too many). But gameplay should be purely practical, easy and intuitively to use and balanced (and we're far away from being balanced but this will be a main goal in the beta phase AFAIK).
So for me the phases of a game should have a gameplay impact to have a reason to exist. RTS games are often divided is such phases like building up resource infrastructure, building up decent defenses against a possible counter attack, and than the (main) expand and attack phase. In the German RTS wikipedia side it's described about as I see it.
Edited by FeXoR, 12 May 2012 - 06:22 PM.