If you want a limit that works --limit the airspace flown in.
larger models have EVERYTHING to their advantage from a pure physics standpoint.
This includes time- smaller models if flown in the same space ( following the big model like ducks in a row ) - get the same time advantage -but you can't see em!
Limit just time and space and then you set a common denominator which effectively limits size of model.
Don't believe that?
OK, how about an event that is held inside a basketball arena?
Who would do that?
Easy answer - it is already underway .
the new electric stuff is self limiting in size -simply because an indoor event limits it.
If you think this isn't real fun -with real skills -guess again.
The products used in outdoor events are driven by the sponsored , winning setups .
that says bigger, newer, more money spent.