Roland's can quite easily replace styles in the ROM area.

Unfortunately, due to a dumb design limitation, you can't rename them... If you are content to remember that StyleX is now StyleY (and just use registrations to call them up) it's not a big deal, but for most of us that would get confusing, to say the least. OTOH, most of the styles are named undescriptive names anyway, so Sunshine Bossa could be ANY Bossa, and no-one would care (unless someone else sits in on your G70!).

BUT.... one thing you CAN do is edit the ROM style to exactly the way you want it, including OTS's. Re-voice it, remix it, change some of the style Parts to different Parts, etc., and then replace the ROM style. Outstanding!

Not quite as good as the Korg's method, true... but not exactly chopped liver, either