I'm trying to have things simple, which is one of the regions the original caps were 50% and 25% - halving is a mathematical operation most of us can do without thinking too much. And halving it for cavalry had some IC logic - you need to store two creatures: The soldier and his horse.
But it's still an additional complication, at a time when we are explicitly and avowedly trying to make things simpler.
I still shudder at the thought of someone having 200 (in a level 4 RC) SF available at once. That's a massive amount of something that should be somewhat rare. 100 is still lots, 150 (my 75% proposal) is massive.
As others have said, that would be a very, very rare occurrence.
There are almost no level 4 RCs of any type, and I think that few realms would raise an SF center beyond level 2 because they take so damn long to fill up already, they would effectively never get full.