There’s a free version of XC8, which I haven’t tried, but suspect the difference in efficiency between the free and paid version are much greater
than between the paid and free version of XC16.

XC16 is GCC which Microchip only charge for the use of optimisation options, which is rude, because Microchip didn’t contribute anything to GCC.
That said, you can always compile GCC yourself.

It’s a dream, and I’d never use PBP for a 16 bit pic even if it ever was supported. PBP will never be as developed as GCC.
The difference between C and BASIC isn’t the same as the difference between RISC assembler and BASIC.. which early on,
was the general choice you had to make for 8 bit pics (whether the BASIC meant PicBASIC or BASIC stamps).