RE: Bi-plane aileron set-up with 4 servos? brain teaser.
I'd have to go with plan "B", also. Most radio mixes are set up for dual servos to operate left and right ailerons, so "Y-ing" the two right servos to one channel (1) and the two left servos to another channel (7) would make radio setup easier.
But why use 4 servos? Put two servos in one wing, and make a mechanical linkage from bottom to top aileron on each side. Super Stearman, WACO, Sopwith Pup, SE-5a all are done this way, plus many others. Cheaper, less battery power used and less weight out in the wings, too.