Noone's done much of anything with this platform. I have done an AWD conversion, and I believe I am the only person to do any significant drivetrain conversion, period. And AWD has its issues. There were some funny car RWD dragster capris way back in the day, but they were tube frame. Plenty of other chassis have had major conversions (there are a few good mid-rear Honda conversions)
Yeah, you're gonna have to come up with something different for the soft top. I was going to run a solid rear section with a vertical window (MR2 / Del Sol / Fiero style) with a removable targa top. Or do a custom soft top frame. A major conversion is not without compromise or issues. (there is no "moving" the gas tank with RWD - fuel cell and lose the trunk space, or low fuel capacity, or complicated custom saddle tank)
Yes, you're going to have to do a lot of fab work to get an engine to fit back there. But it's significantly less disruptive to the whole chassis to stuff an engine back there, than it is to have to cut out the whole ass of the car PLUS have to cut out + add tunnel. These things flex like crazy to begin with, before even cutting into them. Try putting a hard top on when the car's parked on anything other than level ground!
"Integrity" lol. A roadster is a 2-seater, RWD 'sportscar' by definition. The Capri meets none of these criteria. It never 'should' have been RWD, it was meant to compete with the Miata but on a totally different level - it was intended to be a sporty car for young women, and that's how it was marketed and sold. It's an economy convertible built on a economy chassis, and the target demographic did not care which wheels were spinning.
Again: talk, talking, talk.