Put the motor and drivetrain in the trunk ala VW Beetle
Funny you mention that - that's how they do it to some FWD cars, like Honda CRX and Geo/Chevy Metros that I see from time to time on the strip. Moving the weight rearward helps will more favorable weight transfer on a hard launch. Though may not be as favorable or forgiving when you start to toss in quick transient stuff.
There used to be a shop that did FWD to RWD conversion for a number of people. Took typical clean, larger FWD cars, like an Oldsmobile Alero - gutted the car, welded up seams and cut out the front/rear subframes, then dropped the resulting reinforced unitbody "shell" on a modified Chevy S-10 pickup frame. Lots of fabrication and hours to get it there - typical rolling chassis with owner spec'd roll cage runs between $35K-$50K.
New thing now is stuffing older Ford Focus cars with Mustang running gear - very similar process as above. Basically Mustang on the bottom, Focus on top.