Smoky, the washout is a better idea than relying on aileron reflex. While it's true that reflexing the surfaces reduces the angle of incidence compared to the inner portion it also alters the airfoil shape to one which is not as stall resistant. So you gain some, you lose some. On the whole you gain more than you lose which is why it works... to an extent. And it's certainly better than nothing. But if you build the proper washout twist into the wing and keep the aileron neutral where it should be it's all gain and no loss. Plus you don't get folks asking why the ailerons are "like that"....
The other thing is that if you use flaps consistently for takeoff and landing the flaps being deployed also induces a LOT of washout twist in the wing. Even a few degrees of flap will do as much or more than a couple of degrees of washout. And if you wanted to make dead straight panels instead of building in the twist I'd suggest you droop the flaps a couple of degrees instead of messing up the outer airfoil with reflexed flaps.
The choice of airfoil is open for a lot of variations. And if some of the hack duty for this thing will be casual aerobatics and a fair amount of time inverted I'd say that the symmetrical airfoil is a slam dunk good way to go. And make the wing straight and use flaps to add in washout effect for takeoffs, initial climbing and then landing again. In between it can be a blast. But if' it's more for casual upright flying around and letting low timers and raw newbies get a feel you may want to consider more like a NACA 2415. The shape and thickness are known for having good flying characteristics. And the 2% camber isn't so much it will wreck the aerobatics side to a great degree but it will certainly favor a slightly lower stall speed and better manners for slow flying. And the thickness will tend to turn minor stalls into more of a slight mushing which can be easily recovered with a whiff of down to get the speed back.