This seems pointless. The fact that it's not primarily a chat app means nobody is going to use it for day-to-day messaging - you already have to have payments in mind before you start a conversation. So if you want to use it to request payments for an existing group chat, you've got to switch context and invite everyone into this separate chat app just to allow payments.

Or you can just drop a paypal.me link into the chat you're already having.