If you're going to be installing new wiring, I would add a NEMA 14-50 socket on the inside right of the garage, right by the entrance. That location allows for a very short charging cable to the car and also allows for easily charging a car outside the garage door. Just use a plastic hose hanger for the cable. The Neutral wire (in addition to the Ground) will have a negligible increase on installation cost. NEMA 14-50 seems to be becoming the de-facto standard for EV charging and is used in RV campgrounds with 50A service.
I would then simply find the cheapest portable 240vac EVSE you can find, but I would be tempted to future-proof it by getting one that handles 32A and has a NEMA 14-50 plug on it, recognizing that our i-MiEV only draws about 14A at 240vac. You already charge your i-MiEV at 8A using a 120v 15A outlet, so why not continue doing that and simply have a single 240vac EVSE and share it between cars when needed?
Prices keep dropping and I see that 16A 240vac EVSEs are now down to about $150.
Here's a 32A 240vac EVSE for $235 on eBay with 14-50 plug -https://www.ebay.com/itm/EV-Charging-Cable-32A-Electric-Car-Vehicle-Charger-EVSE-J1772-NEMA14-50-Display/383368051084
, although I personally prefer portable EVSEs to be dual-voltage and have adjustable current for versatility on the road.