I would like to mention the importance of uptime.

Having a working system to charge customers with an uptime of 99.99% is key. Get the merchant losing a single sale because, for whatever fucky reason, the payment system doesn't work, and you will lose their faith and interest. To make a solution in the fashion of self-hosted node + BTCPayServer reach that uptime performance you need to be a master sys admin... which I would guess 0.00001% of merchants out there are.

I'm not saying merchants shouldn't self-custody or run their nodes. But perhaps the ideal combo should be (1) an outsourced payment gateway with PERFECT uptime and experience that allows withdrawals in real or near-real time and (2) the usual bitcoiner self-custody kit to collect revenue into safe, self-managed keys fast.