An E93 is definitely a great compromise car if you want something that can serve as a very good GT car and still carry itself perfectly well on the road and even pretty well on the track. I just don't drive very much to see the sights, I guess -- but keep in mind that some tracks and/or HPDE organizers don't allow convertibles of any kind, and I believe that includes most if not all CCA chapters. As for damage at the track, I'm lucky in that my insurance carrier (at least in Texas) covers driving on the track as long as you're not practicing for or participating in an actual race, but there are also independent HPDE insurance carrier such as Lockton that can cover you if your regular insurance doesn't. That of course adds significantly to the cost of the event, but per an earlier "M School vs HPDE costs" thread, you'd still be spending a lot less.
But for me, I figure that if I damage my car on the track while covered by my normal carrier, unless the repairs are in the high four-figure range I'll probably just pay out of pocket to avoid a major insurance premium spike and possibly a "We'll cover you for this but we're not renewing you" situation. Of course having dedicated HPDE insurance avoids this whole issue. But at the end of the day, avoiding damage is mostly a product of knowing your limits and expanding them gradually. Keeping MDM on can also help. With a sufficiently lenient computer, as long as you're mindful of when it intervenes and make a mental note to consider adjusting your driving style in that spot rather than continuing to drive poorly and letting the computer smooth you out into a rockstar, I think keeping the nannies on can work. And now that I've coded Euro MDM, I've got that exact setup of the computer stepping in only when I've really screwed up beyond being able to save it myself and am therefore grateful for its intervention -- otherwise it lets me do my thing.