All these alternative ideas sound great, but from personal experience I can tell you that getting anyone to start using an alternative method of payment just to use your site, you are fighting an extremely uphill battle........escorts to pay for ads which were actually superior to their existing options and they went nowhere fast.
Even though you offered superior options, they still had a way that worked ok for them and that's what they would stick with.
I would think BP is not just another site to escorts.
Although UG and other sites of this type are useful to escorts, BP has several major advantages to escorts that may require them to find alternate means to get on BP.
Off the top up my head:
1. sheer size - I'm guessing but maybe a couple of orders of magnitude more "purchases" of escort related services generated than the sex sites.
2. Not blocked - many places offering free internet access will block sex sites. This happened to me recently when I was out consulting at a company and wanted to look for a lunchtime "snack". Didn't allow UG but did allow BP access.
3. Legitimacy of visiting BP or CL: I know of some grandmothers who use it. No problem with BP or CL showing up in autocomplete suggestions that pop up on a computer's browser that may be shared by other non-mongers as there are many legit reasons for going to BP or CL.
Just for perspective: when UG was doing a request from site users fund raiser a while back I sent mine in via a totally untraceable way (forget if it was cash or money order) as I do with my burner phone minutes even though it is 5% cheaper to buy minutes via my Target credit card (I may be paranoid but doesn't mean they aren't out to get me). I would think if I was willing to do that for, ahem, solely altruistic reasons, someone (both BP and the escorts are in the category) whose very livelihood depends upon it have strong incentives to find a way.
As you say "Perhaps I am wrong and time will tell" - wouldn't be the 1st time I've been naïve in terms of the supply side of the sex business.
Should be interesting to see what pans out.