It'd be a glorious swap, and besides the amount of trouble engine swaps routinely are, this one could be above and beyond. And from living with the Civic for the last two weeks, worth every drop of sweat. You wouldn't need the IMA at all- if the Civic has any lag, it's been dealt with. Hence you could get rid of the battery and replace it with something silly, like, oh a spare tire.
I just did another one-bite Sacramento-to-LA-to-Sacramento concert run in the Civic with fifteen hours of road time, and could have done more. The Civic isn't quite a monster, but it's very quick. First time I'd felt torque steer in a car from this century.
If Honda would have started the CR-Z with the power plant now in the Civic, they may have had another 240Z phenomenon on their hands.
I suppose the first step would be to measure the engine rooms and the engine packages....
And after that, the fun would start. Control units, transmission match-up (you'd want to use the complete Civic package if you could, but you'd want the shifter paddles enabled), fuel, exhaust, cooling.... the usual engine-swap center ring of the big circus.