I'll have to try the regular resolution mode again - which looked great, but I'm so used to the original look, it's very difficult for me to go away from that. For career mode, I was thinking about something more like Super Monaco GP for the Genesis - it has a fairly simple career mode where you earned money from sponsors, which let you then buy upgrades. By career mode standards, it's pretty basic, but for replay value it's great - although you already have a really good leveling up system as it is. It was just a pure wish-list type suggestion, but if you get a chance, maybe checkout that example and see what you think, if it makes any sense or not.
Also, again, the Test Drive flashback was awesome, and completely unexpected. I played that game so much as a kid, to come out of the tunnel and have the mountains there - that was just amazing to me. Just a fantastic job - I love it!