I had a 1995 Yamaha TRB6 with the "thin" pickups - which were in have split humbuckers - not in the least bit "thin sounding"... I replaced them with Bartolini G6's and the sound was incredible....
My idea for the old 1306 was to do something very similar, probably with Nordstrands. Carey will do a custom pickup as per my sonic requirements. Bung in an updated preamp and I'm away to the races.
But yes, to your point WRT "thin sounding" thin pickups, I concede there is a lot of truth in that