There is a huge problem with the concept of not "aging up". This is the HC. Or you start in a later age being able to send military shipments from the start, or you are limited to about 9 cards. To solve this some sort of aging up must be detected. If it is possible, maybe number of shipments sent? 2 --> II 5 --> III 8 --> IV 15 --> V ?
Also, for the resources problem: why not be able to train gaia animals/objects? You could make them spawn I think by doing this: invisible unselectable object trained, it flies away and quickly dies and spawns a herd/some trees/ a mine. This way these civs will maybe have very fast resource gathering for a long time, but their gatherers will always be spread out and not close to the TC. In ffa this will force you to attack your neighbors; however there must be a way to not make such civs spam animals in team games. So most probably the invisible unit should be made rather slowly, and probably should move slowly (and live rather long). That way it should not be viable in the beginning of the game, and would not be very viable for helping out team mates.
IDK, but I have the feeling they shouldn't use the default line tactic, but instead the spread out (volley??) tactic. This will have the benefit that their mostly infantry armies will last a bit longer.