I wonder if this requirement can be sidestepped by shipping the customer something, but just not the actual item being pre-ordered. For example, emailing them a redeemable code or physically delivering a voucher.
If not, it seems like you could go even further and bundle something small but tangible with each sale. For a game pre-order, maybe access to a demo or access to private forums?
I would think that you could negotiate this with a merchant bank. For instance service companies often take deposits and kickstarter clearly charges before shipment. But in both cases they probably have agreement from their processor for their business model. I think having to post reserves is one such model for when you are doing riskier transactions.
But don't think that merchant bank won't cut you off if you violate the terms of your agreement.
However in practice merchant banks seem very lax compared to PayPal.
If not, it seems like you could go even further and bundle something small but tangible with each sale. For a game pre-order, maybe access to a demo or access to private forums?