First that I have heard of ice blasting but sounds like a good idea.  I would certainly stick to a mechanical removal method to avoid possible damage to the gel coat from harsh chemicals.  In 2017 we were given the job to complete the stripping the bottom, barrier coating and Copper Coating a 45’ Ketch (non Amel).  The owner had been using a water based stripper from West Marine which said right on the package that the product was safe on gel coat and had thrown in the towel when he realized what a big job it was.  We began dry scrapping  (using carbide bladed scrappers)  the hull bare and began finding numerous areas where the gel coat had softened significantly, right down to the glass.  We tried washing the hull with soap and water numerous times and allowing the bottom to dry but the gel coat remained soft in areas.  In the affected areas, the gel coat acted like hard chalk that would turn to powder under the scrapper.  The gel coat on the parts of the boat that were not being stripped was hard as glass.  In fact the hull topsides are of the original gel coat finish, not painted so this softening on the bottom was definitely due to the stripper.   We ended up dry scrapping the paint off and then machine/vacuum sanding off all of the gel coat right down to the glass.   We even found some minor softening in the outer glass layers.  Keep in mind that the polyester resin in the hull is very similar chemically to the gel coat.    Now it is true that the owner of this boat was not following the instructions for the stripper in that he left the material on the hull for an extended period (months) so certainly this was a factor.  But the fact of the matter is that there are strippers that can do permanent damage to gel coat and I personally would not take the chance of damaging such a large part of the hull to save a little time stripping a bottom.