Since the mixer is built into the contol board, I think you would have a very hard time trying to eliminate it. It would not be done at the three lines to the servos. You would have to isolate the part of the circut board that has the mixer logic and somehow bypass it. I don't think it would be worth the trouble. Most likely you would destroy the board.

Why not just take out the guts and go to a standard receiver and servos? You would need a radio with 3 channels. With a 4 channel radio you could leave the tail alone and just turn on v-tail mixing. Then Ailerons go on the 4th channel.

However you are still dealing with an undercambered wing which will resist inverted flght. Also, since it is foam and not supported to accept aileron input, you will have to reinforce or replace it with a stiffer wing, otherwise it will flex a lot when you give it aileron input.

If you want a plane with ailerons, I would not modify the aerobird. I would go to a new plane. There are lots of kits or ARFs in the $40-60 range that would be much beter suited.

However if you do go forward with your project I would love to see the results.