The problem here is the siren's call of "give me your money, and I'll let you play this game". If you do this, then you have to play by the existing rules.

The solution is to shed the idea of taking people's money and creating software for real p2p trading. Operate your own trading engine and hold your own keys on your own server. Find your own trading partners (Telegram, forums, etc.) and settle trades using interchain or intrachain atomic swaps.

No risk of stolen funds, no risk of the counterparty cheating. No need for accounts or third parties.