I think you should have eight man teams, eight riders to a heat, two heats of sixteen laps. Points scored are 8 down to 1. Any eight riders for each side would do. ( A bit like meetins before a grand prix weekend)
The meeting would be over in fifteen minutes, twenty at the maximum. The aggregate scores of the team riders would provide the result. No re-runs for falling riders. If a rider comes off 1 point is given to the opposing team. Race would not be stopped but simply slowed down to allow the debris to be removed from the track.
In event of a draw the fans can nominate riders on leaving the stadium (no postal ballots allowed) and after a recount the following morning the BSPA could declare a result. Save problems with the weather, ballot result could be declared by each promoter having a vote.
The paying public would get to see 32 laps of speedway for half the price and still have time to do something else in the evening.