Bit of a brain-dump down below here (which I'm prone to do after a few espressos
), and I freely acknowledge that YM(and opinion)MV.
Re: doing a swap while turning the car into a pure track/race car
Based on my experience, for reliability while leaning hard on the car, that would argue for a motorsports-quality standalone ECU (e.g., MoTeC GPRDI-M182 at ~$8K) and a custom harness after removing whatever was necessary from the car to accommodate it. (The more the better in that regard so as to reduce the car's overall weight.) I don't know what that would cost, but in the early 00s the custom mil spec wiring harness and connectors in my E36 M3 race car cost $22K. Crazy, right? But the car won a pro-am championship and was reliable as a rock when I ran it in time trials and during track days. From what I was able to learn, the car's only DNFs during its four years of racing Motorola/Speedvision Cup and Grand-Am were due to wrecks.
I'm not sure what the point would be of pouring money into a heavy car like ours for that sort of duty. One of the problems is that these cars can't be made light; they're going to be heavy no matter what we do. Who's going to want it when you're done with it; used (used-up, more likely) track/race cars aren't worth much at all, despite what some owners imagine when they first offer them for sale. For example, I sold my race car for $32,000; the race shop informed me pre-sale that to duplicate the car starting with a $5K E36 M3 would cost $150K. That did not come as a surprise, and I was pleased to receive $32K for the car, even though it was in tip-top condition, unlike 90%+ of used race cars out there. I don't want to think how much money I put into that car – if I could get that money back and give the TTs and track days back, I'd have enough for a GT3, most of the days at the track, and a major upgrade in the neighborhood I now live in (which itself isn't too shabby).
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Re: doing an engine swap for an F22 that's going to continue to be used on the street
tldr; Keep it simple – just hand your bankcard over. Seriously. My perspective is having the swap done by professionals who know what they're doing, have done it before with a contemporary BMW, charge an appropriate amount for the quality of the services they provide, and hand you a car back that has or is soon going to have problems. IOW, a seamless conversion, which is much harder to achieve than it might seem. For me, a non-handy person, this is not a DIY project. I've seen what those frequently end up looking like, and they were all much simpler than this would be. Completely off the top of my head, I'd suggest something in the neighborhood of $25-30K at a minimum to swap something into an F22 that will then still be just like it was but with the new engine. That's a semi-educated guess, so take it for what it's worth, as prices, complication, and unforeseen problems may not be what I'm projecting. After that, of course, there's suspension, wheels and tires, brakes, built diff, trans and diff coolers(?), and on and on and on.