The cost of used turbo kit is really not that much more compared to a good top swap, cam, headers, and tune. If he went supercharged he would more than likely do those as well. So why waste it on going S/C? It won't matter if he goes turbo or S/C anyways they way he is talking he's gonna need a trans anyways.
If you are looking for insane power on this platform than yes-turbo is the way to go. And no the kit isn't that difficult they are all bolt on.
If he does a top swap and wants to put down power he's going to need tires regardless. Turbo cars are finicky in heat? Please explain how they are more finicky than a M90 in summer? I live in Texas we get 105+ temps and my turbo car is as finicky as it was Supercharged.
And you could have spent about $700-$800 more dollars and gotten a good used turbo kit-ready to bolt on and go. By as long as you are happy with the M90 that's all that matters.