Michael
@Jack, was the second suggestion in the poll ("Give League Hosts an option to...") ever considered as a possible implementation? So saying it another way, can we hope that it's going to appear one day or is it too complicated?
We think this kind of stuff is best reserved until we have a friendly/casual race system, and offering maximum flexibility within that system. It will be well suited to a wide variety of custom parameters, and players could even create their own leagues out of the results from friendly races if they wish.
Leagues organised within iGP should be a structured, hierarchical way of progressing through the game. If all leagues vary wildly it undermines some of the comparisons that can be made between leagues and between ranks in the HoF etc.
As for when casual races will be added, we don't know yet, because we've wanted to get scaling issues resolved first so we can ensure the quality of the overall service won't deteriorate with erratic load being placed on it. It's a big challenge, but that's why we're doing a service migration soon.