Just a few options I would like.
I would be nice if it could save league progress, such as the league table, everyones lap times, replays of each race (editor please Kaz),replay of the fastest laps.
Another option regarding league's would be practice sessions. Each player could be limited to three one hour sessions in the build-up. These sessions would be available for 6 days or until qualification and race day. It would save your 5 fastest laps per session for viewing by others, and could be put on youtube as a collection. It would edit each lap into a vid split by a screen with the lap time.
I was thinking that a parc fermé system could be imposed, so once you enter a league and have chosen a car that fits the rules, you lose this car from your garage, and you get it back once the league is over or you quit the league.
This would be used for preventing people practicing offline. On it's own it would be pointless, but maybe you could have a league contract, if you sign for my ideal GT5 league you would allow your game to block you from racing the same car outside of the league. Again it would be just a option and wouldn't be mandatory for leagues.
With damage being included, it would be cool if limitations on the number of gearboxes and engines per season like in F1.I suppose you could even charge credits if you wanted.
I think it will be a feature, but a mandatory pit stop option, I'd like to set certain number of laps before fuel can be added, I'd be surprised if that's not in though.
I do have other ideas but it would drag on a bit