But processing payments on behalf of others and taking custody in the procesd might require a money transmitter license in your jurisdiction.
That's quite dumb actually. "money transmitter license" is for "legal tender" not for Bitcoin. But people are dumb and just get scared and follow orders like sheeps. And I answered the same aspect here: #329364
Quote from EU regulation
This Regulation shall apply to transfers of funds, in any currency, which are sent or received by a payment service provider or an intermediary payment service provider established in the Union. It shall also apply to transfers of crypto- assets, including transfers of crypto-assets executed by means of crypto-ATMs, where the crypto-asset service provider, or the intermediary crypto-asset service provider, of either the originator or the beneficiary has its registered office in the Union
Would you agree the LSP is temporarily taking custody?