First let me clarify that it's not "my" software. I am a user just like you, I'm not part of CC. Having said that, there's not any type of integration for a login system nor do I ever believe there will be. Reason being because in order to do that you would need to collect personal information to setup accounts and the software will not ever be collecting personal information.
You "can" however, alter the files as you've asked about, that's something totally up to you. Do be very aware that any changes you make may need to be redone every time you update your shop as it would most likely overwrite those files each time, they cannot be imported in at all.
Someone here may have some ideas on what you can do for this integration, but it's not ever going to be part of the software itself, I'm pretty sure of that simply because they don't want to deal with the security procedures required in order to collect the personal information involved for purchases. I doubt very much they will change this system just to collect "partial" personal information to setup accounts. But... I hope they surprise us both and work something out for this as I know you aren't the first to ask for some way to setup accounts, wish list type systems and favorites type systems.
I open the floor to anyone that has the knowledge here that is needed to do this, that's far above my pay grade
