I must agree with Rich on every word. I have seen a lot of people with huge problems with the tamiya units (specially making the cannon and machine gun shoot) and many more with ibus, clarks etc, so I can imagine how hard will be for most of tank users to buy your board, ESCs, benedini board and make it work together.
IMHO (and I might be wrong) if you want to succeed with your board, it should come with the ESCs and be able to play sounds. The benedini is a very expensive board for what it is, and most hobby grade boards have way superior amount of sounds and quality just for a bit more cash.
Anyway I think the open source is a great idea, and maybe soon you can make another board with all the functions what we need.