Orbot + NetGuard
You guys may want to check this out: NetGuard is an opensource no-root Android firewall that supports SOCKS5 proxy. So basically it already has ability to torrify all android apps, while filtering their traffic. Here is related discussion:
There is one main developer who works on the project at the moment, not sure about quality of his code or ability to work in a team. But you could always fork it and take both Orbot and NetGuard to the next level.
Project's home page: