I've had my Metro for about 5 years, with 3 years of consecutive driving. I moved from a relatively flat area to the alpine mountains, trumped by Subarus and Heavy Duty Diesels. The Geo is great! The winter conditions forced me to learn how to control my FWD car without 4WD. Fuel economy is outstanding; about 35mpg. I can put $20 in my tank and run about 2 weeks, or about 280 miles.
Thicker fenders and exterior plating. Maybe a rollcage feature, other than that, not really a whole lot. I'd do some upgrades on the seats and the interior. Lower the dash height, extend leg room, pull front headlights from pockets so faces are flush with front of car, instead of inset 4 inches.