I have some ideas here:
-All trees harvestable(that's not my idea,but i've put anyway)
-wild animals or units that would attack any player(like dangers of the forest)
-ability to trade resourses with allies(like commerce)
-one or two more factions, maybe something intermediary between tech and magic
-treaty screen
ex:
1 2 3 4
1 at x t
2at xt t
3x xt x
4n n n n
Legend: a = ally x = enemy t = allow trade(even when enemies)
n = neutral
this last one would be a cool thing to have in glest