Sorry to bring the thread back up, but I'm curious about why the Sonic would be so hard to supercharge? Apart from needing a custom intake manifold and needing a new tune (Which is true of supercharging any naturally aspirated engine), everything else seems pretty simple:
-Vacuum lines could still be run before the blower and after the throttle blade, which would still provide the same "vacuum to atmospheric" range as normal.
-Shortening the spark plug gaps, or going to a way hotter coil will prevent the increased airflow from blowing out the spark event.
-Aluminum tubing could be routed in the stock inlet location.
-There's ample space to feed a lighter blower off the accessory belts. Or worst case scenario, getting a blower pulley off the crankshaft wouldn't be too difficult.
-There's already higher flow-rate injectors.
-Most superchargers don't need an intercooler below 10psi, which would be far more than the 1.8 could survive anyways. Hell, even if one was aiming to go past 10psi, a water/meth injection kit would be way more than capable of dealing with it.
Way I see it, going to a small blower like an M45 or an underdriven W100AX should be fine, provided the actual rotating assembly is up to it. The W100AX in particular seems like it'd be the easiest option to manage:
1) Buy the blower, and find a spare intake manifold at the junkyard to modify. Exchange injectors for higher flow variants.
2) Once mounted to manifold, take off pre-existing manifold and exchange for blower & manifold.
3) Measure the distance required to get it to the crank snout, and buy the appropriate pulleys and snout.
4) Route a path from the back of the blower either to the original fender wall, or to new location.
5) Update tune as required, or use self-tuning ECM.