Sponsor lists should be allowed, it would be denying a sponsor their right to advertisment.
I personaly feel that the mains should be run by class, not letter. Most of the time a driver runs multiple classes they will be in the same (maybe 1 apart) letter main. Why make it more stressful on the racer, and add delay into the program to wait for them. Simply run the mains by class and it would flow much better.