The rental companies from the French side would not have the "R" plates and there are some companies on the Dutch side that seem to offer both so it is possible to NOT get them. Regarding the deductible you had to face, I don't have an answer to that but I believe there are some policies, AE premium coerage perhaps, that offer first dollar coverage for things of this nature.
The following is purely an opinion so please take it as that and nothing more:
Personally speaking, I don't think it really matters what kind of a plate you have on your car. Over 35+ years and who knows how many trips, we've rented both and once in all those years did we have a problem. Yes, we had the dreaded "R" plate that time, but honestly, I believe the nature of the plate had a lot less to do with our problem than the location in which it was parked - Mullet Bay Beach parking lot and further back from the main stream of traffic in and out of the lot. Usually we get there very early in the day and park in the front row closer to the area the concession workers are but this particular day we went in the latter part of the day and had to park way in the back.
The reason I think this is so is because all the cars around us in the immediate area where we were parked were broken into and one or two others had the R plates like us but a few more had the French plates and from the appearance of a few of the cars, they appeared to be residents cars as opposed to rentals.
I think the choice of cars to break into had more to do with the fact they were in a location where the little creeps could hide in the taller grass and brush and easily access our cars when no one was looking than the fact they had "R" plates. This was the first (and might I add the last) time we ever parked in that part of the lot and it was the only time our car has ever been vandalized on SXM. And truth is, we never leave anything in the car so all their effort was for nothing beyond causing grief for the rental car company.
I know it's easy to blame the problem on the R plate, but honestly, I'm skeptical of that and think it has more to do with time, place and opportunity.