I think it's ok to borrow from multiple sources, if this helps bring over all interest that is being paid. And usually friends lends money with little to no interest. Id do that to manage the debt. But for no other reason.

I guess your friend has made a mistake somewhere if he is stuck inthe money rotation plan..

Rule 1 is always be clear from debts. This is something I had learnt the hardway. But a lesson for lifetime.