Great idea, there are some issues I see for example there is no connection between the trade signal and the actual trade in a trading platform. I prefer the idea of copying in websites like 1broker more than just seeing something in one platform and doing trading in another one.

Also for tech stack, I suggest to go all JS stack for a good reason. Steem-js library is developed by our team and polished by steemit team, make it very stable to deal with it and would have all functionality you need. Also for future growth you wouldn't need to hire python devs and react devs individually since every react dev can work on a node stack.