Implementing new ships would be easy enough, but adding online isn't something I'd plan on doing. I know Game Maker is capable of it, but it seems like a lot of trouble to implement.
The track is built entirely out of objects, with the AI ships randomly switching from a number of set paths at certain points based on a dice roll to give the impression of more human racers. So the AI are really only objects set to follow a path and move out of the way of each other.