Then you have some reasons why you could benefit from not having a cost averaging. But for many people for whom insurance does make sense, there are benefits to MSP as well. Part of my reasoning for not wanting to enter the turbine world is the uncertainty with operating costs (where $70k+ parts are common) and many other operators feel the same. Since you're also looking at self-insuring your plane, you might not fit into that catehory. But I also have insurance and would much rather pay the premiums I never use than risk a $100k+ botch-up, or just having a $70k fuel controller go out on my TPE-331 (if I had a TPE-331). To call those who sign up "suckers" I think ignores some of the realities they may face and what might make more sense for their requirements. Also, turbine engines have the advantage of more consistent operation and tolerance to varying operating modes.
You are correct at the problems with doing it on a Lycoming or TCM, hence why I say a FADEC would about be a necessity and some structure that keeps people honest. I wouldn't be interested in a MSP-esque setup on pistons personally, but I know a bunch of people who would...