Lets not kid ourselves; the only reason a "pilot" is suggested is because some people find the whole BA-popping-out-of-a-'mech is silly. Sure, it is a bit silly, but being forced into a terribly weak role simply to preserve the illusion of how battlemechs actually work is even more silly when considering gameplay.
Not to mention the amount of time and effort it would make to create, program, implement and bug-test such a massive change in game design. There's enough complaint about how long it takes to get into battle, how much more do you think that would be magnified if you're stuck in a role every time you die or eject that's both easier to kill and less maneuverable than Battle Armor is? (Giving pilots MORE maneuverability than BA falls into the same trap of silly & not-making-sense, so why even bother changing anything?)
Dedicated BA options are already available, and will only be expanded upon in the future. I'm with Invictus in that I don't see any justification for such a radical change, except to appease the BT purists.