is there a tool like NSFimport for GBS files? interested in looking at the specifics of some game boy tunes and simply splitting the channels isn't working out too good for me right now (it's good but not nearly as accurate)
Tweak is an understatement. It'd be the same as writing another NSF import from scratch.
(However, I am currently writing a text import mode for Famitracker, which should hopefully make these kind of import projects easier in the future. Will no longer have to hack stuff into a build of Famitracker.)