If you have it soda blasted, it will be a matte finish, but intact gelcoat. You may be able to shine it up.
A 36 grit grinder will strip it down to the gelcoat, but it will rough up and likely remove some of the surface of the gel coat. it will not take long as the antifouling paint is real soft.
If you go this route, you will want to paint the bottom for appearance. if trailering a 1 part polyurethane will work. Obviously you will want to sand it to 80 grit before painting. Roll and tip of the paint is pretty good.
You are correct in all you stated.
Allow me to clarify a few things,. about my reply.
1st. I was using an orbital Sander, not a grinder. (big difference)
2nd. it was electric, so again maybe not as aggressive as a good air version.
3rd. my plan was to get through MOST of the minimum if not thicker than 1/8" layers.., then ease up with 80-120 grit. again it was thick as 2-4 layers of fiberglass.,.(part of this I didn't clarify)
4th. My particular situation was a pretty challenging, old and many layers.
and I made it clear a re-gel was to follow so not so much concern about a few scratches, as you have a whole different prep process for that. going through the gears.
I should have been more detailed, and yes 36 grit is aggressive, I took it for granted this was already understood.
Sometimes 1 forgets, not everyone has same exposure to smaller unexplained details,
And we are hammering this out from a keyboard. so a lot can be missed as we short hand explanations.