I assume you mean elevator halves travel same direction as ailerons? , with this mix , is the only aplication faster roll rate? , and this should be on a switch or do some guys leave it permanently on?
Correct, mixing reverse would be interesting, but probably useless and maybe unflyable. Set up as flaps so they move a fixed amount, it could possibly REALLY slow you down alot.
As far as moving the same direction, some of the military fighters use this also, watch some carrier landings and you can see the elevators working for roll control. It would be most benefitial for really slow/stalled stuff, it just gives you some more authority for the ailerons.