The problem with controlling supercharger boost using bleeds and bypasses is that the efficiency takes a nose-dive. I've heard of a few variable-speed drives, but they themselves have a variable efficiency below 100%, so you'll lose efficiency there as well.
That being said, if I were to put in a relatively mild F/I system in a Civic, I'd go the S/C route. Go up to 10-odd psi, no intercooler, a bigger exhaust, and a bypass valve for low-load bypass, or a clutch. As for the choice of S/Cs, the best IMHO would be the Lysholm-based screw superchargers (KB, Autorotor, Whipple et al.), since their thermodynamic efficiency is much better as compared to the Roots-blowers as found in the majority of superchargers. Higher thermodynamic efficiency means that it can increase pressure of air without raising its temperature as much as with a Roots supercharger.
Why a S/C? Quick response, negligible heat shielding issues, compactness, and that S/C whine