Something I'm actually trying to do, but currently hit a roadblock (since I've trying looking for helmet graphics in the ROM to no avail):
Super F1 Circus 3 (SNES): Replace David Coulthard with Ayrton Senna, considering Roland Ratzenberger is in the game. Alternatively, I could keep Coulthard in and replace Ratzenberger with Andrea Montermini, considering he was Ratzenberger's first replacement driver - except everything in this game seems like it's developed during the first few GPs (Simtek having their testing livery with no MTV sponsor logos on the team list during startup, McLaren and Sauber having their 1993 liveries for some reason in the same sequence, etc).