I see the 'promotion/relagation' thing appealing to new, or newer fans,,, maybe get a bit more media coverage at the time, and some might 'relate' to it and come along and watch, wether they come back or not is a different matter.
Getting more fans thru the door is essencial to speedways survival, (long term). I think its a good idea, wether you 'throw' a match, or not at the time, wouldn't be that obvious to most 'new fans', if any do come