If you do go ahead with your turbo Civic Hybrid plans, you'd probably be the first HCH turbo owner, but you'd be the second Honda Hybrid turbo owner I know of. There's a guy on Insightcentral.com that has a tiny turbo on his Insight. It's a really primative setup, but I guess it's sufficient given that it was very low boost; I think he's also running around 6psi or something.

It's the stock turbo from the Canadian Pontiac Firefly, which I think was also briefly sold in the US as the Chevy Sprint or something. IIRC, that was also a 1 liter engine, so it's basically already sized for that displacement. He went from something like 62whp on the dyno to 90whp, which is a real good boost. Anyway, I believe he was running a voltage clamp on the MAP sensor so it would read accurately up until it hit the voltage reading for 14.7psi at which point the device would simply not pass any higher voltage to the ECU.

He had a second MAP or something which was read by a GReddy Rebic II fuel controller running 1 injector in the intake just ahead of the throttlebody. Kind of old-school, but if it's good enough for the Mitsubishi Starion turbo (which also ran throttlebody injection) then I guess it's good enough for the Insight. Fuel mileage was barely changed by the turbo since you spend very little time on boost - the main benefit is just having far greater power reservest for merging, passing, and hill climbing.

I suppose at some point, Honda might do like VW did with their newly released turbocharged, direct injection 2-liter 4-cylinder. Between small displacement, a turbo, direct injection, and a hybrid drivetrain, a savvy manufacturer could almost certainly deliver very respectable accelleration performance figures while still returning excellent fuel economy. I would think that the instant torque of an electric motor would help to mask any effects of turbo lag from a small engine, plus a CVT would make it possible to get the engine into boostable RPM any time you put your foot down.