I have no idea what the Mercury teams are using nowadays, it is probably dictated by class rules. Plus the offshore boats all go from a rolling start so the need for extra low end grunt is not very great. Where they tend to have problems is when re-entering the water after getting airborne. You need to roll back the gas on re-entry or you will break the outdrives.
I don't know anybody anymore at Mercury. I got out of the boat business back in the mid 80's for a civil service job with a retirement package. I just retired and got back into the boat business a couple of months ago. I like customers who own outdrives, but I personally own only v-drives at least for the last 20 years (Hallet 20' v-drive mini cruiser).
I think if a guy had the time and the money a fairly decent hot rod outdrive setup could be built. There is a lot of new technology available to improve the gears, and shafts (Cyro and heat treating) in the outdrive but you are still going to be left with the problem of the housing flexing. Currently Mercurys answer to the breakage problem is not so much improving the design or materials used but just increasing the size and bulk of the components. Its one of the advantages of pretty much owning the outdrive market, no competition from another maker to force you to improve your product. As it is now, they are making a fortune in fixing the ones that break...........