The discussion is pointless anyway because we don't know about the changes after wipe and it seems like they were made already.
Well, two things from the previous posts won't be possible. Mercs won't be able to disappear when in battletimeout anymore and you won't be able to leave mercs sitting on maps without thier master. So if you want to camp somewhere you actually have to be there too.
I think there will also be a period of not being able to be hit or move when you spawn into a map too.
As for Mutant mercs, you won't be able to get as many as you can now - and to get to the maximum amount will require a lot more effort than a Ch10 alt. (A level 1 Ch10 alt would be able to get one Mutant, if I remember correctly)
Different Mercs have different requirements, so it would be possible to get a lot of Melee guys, or one of two Mutants, with the same character.