I have read your whole post OP, and I do agree that there are somethings that stock exchanges lack. Anyway, the feature I like most is the copy trading. It's like what e-toro is advertising where the program would connect to the exchange and copy a traders trade. I think that would be a useful feature with every trading program.

I hope margin trading would be included soon enough with your program, and I trade in Bitmex most of the time. I would probably check your GUI and features soon.