U increase the company member limit and not fix the ally member limit.
The mega's do not care about your restrictions, they find a way to organize themselves.
U limit the small companies, because the small's can only allied with 4 other companies, too.
For example:
7 companies with each 4-6 friends share 1-2 island in a grid. That are about 35 player and they can't be allied.
Mega = 5 x 75 = 375 and they could organise the zerg otherwise.