bitartrate I guess the question is how much translation and from which old systems people are looking for.
I've got a good handle on translating tokenized MS basic so it's fairly easy to convert the Basics from Pc BASICA/GW-BASIC, and the Commodore and TRS-80 lines. The tricky bit is dealing with the system specific language features.
The C64's Basic is fairly simple so there isn't anything particularly difficult in the language itself, but what's unique is PETSCII, peeks and pokes that are very common to C64 Basic programs, and file handling. I'm a longtime Commodore user so most of it isnt going to be a big deal. It's nice that the Basic Engine has a built in Commodore style font, but I haven't had a chance to really play with the Basic Engine and I haven't seen any much on how, or if, it handles control characters. As it's worked well in other language translations I've done, I'm going to create function libraries that tack themselves to the end of the translated file which replicates the missing features.
Once I get familiar with the Basic Engine and create myself some reference docs, first thing I write is a C64 and MMBASIC converter. MMBASIC is fairly close to the Basic Engine and the text parser I'll need to write will also be used for converting other non tokenized files.