Not sure if this is possible or if it would cause a nightmare. So I use v4 and multi-store. Let's say my main site is sitea.com and I have an addon store called siteb.com, but host my secured server at safeshop.net, is there a way for people to shop on either sitea.com or siteb.com but be sent to safeshop.net to process orders even though the site would appear to still look and feel like sitea or siteb?
Does this make any sense?
I understand what you are attempting to do, but it's not reasonable to do it that way. You would have to write a custom addon that posted the checkout process to the second server and then post the payment processor result back to the first server.
I guess the questions would be why do it?