Basically, I was thinking that an unlimited companion mod could be easily abused and distort game balance. A very easy way to handle it might be to make the nerve bonus decrease based on the number over the normal limit. Furthermore, at a certain point the nerve penalty actually results in an overall penalty to ally performance. This lets players recruit to their hearts content, while hopefully preserving some balance and retaining the nerve bonus from charisma.

I think with a little work this would be the ideal way to implement an unlimited companion mod.