Sorry to break your bubble guys, but the gosub/stack limitation has nothing to do with PBP.

The PICs do not have a way of 'POPing' the stack (hey, they're extremely powerful for their size - something's gotta give). A GOSUB is no more than a CALL in assembly. When a CALL is made the next address is 'PUSHed' into the stack, when the RETURN is encountered the stack is 'POPed'. So you see, without any other way of 'POPing' the stack you will overflow if you keep nesting GOSUBs.

Not to worry though, amazing programs have been made with these little devices for more than a decade. Just have to be more careful and a little creative.