A V8-powered Dino would be a tight fit, but if you got the engine designed for compact dimensions (meaning 308/328 series) you could make it work.

(Bear in mind, in all cases, I'm presuming the car is engineered for it to start with, & ends up very like the OTL outcome...something I now realize I should have said to start with.

)
A Daytona-powered 308 wouldn't work because V12s are too long to fit in transverse engine mounts
Then I invite you to explain the 365-powered number I've seen in (IIRC)
C&D... (Or look
here &
here. On reading those, however, I suspect saying it was a 365 engine may have been mistaken...

)
The handling bugaboos are a separate issue, & I won't disagree on that.
Better idea might be using the Daytona engine in the Testarossa instead of the Flat-12 and putting the gearbox between the seats as the Lamborghini Countach and Diablo did
I do like the idea, tho I'm no particular fan of the TR.
As far as a four-door Mini goes
The one drawback for me is, it buggers the otherwise near-perfect proportions...
It is possible BMC feared a 4-door Mini (with the wheelbase increased by 4-inches) would eat into 1100/1300 ADO16 sales yet the 4-door Mini could have initially been sold with 850-998cc engines, before later receiving 1098-1275cc engines initially appearing on upmarket or performance variants as ADO16 receives larger-engined variants above 1300cc earlier.
http://www.aronline.co.uk/cars/mini-classic/concepts-prototypes-mini-four-door/
Treat the 4-door like an entry-level ADO16, then? Works for me. (That link's probably where I got the idea.

)
NSU never did figure out how to make the Wankel rotary a reliable long-term prospect, and doing so nearly bankrupted Mazda so I wouldn't exactly call it a great prospect.

I didn't realize it was that bad...