"Does that make sense?"
No, not at all. You are bypassing the best features of FAA. You don't have to do any of that.
Has this ever actually come up?
Not sure where or how you find those few individuals who can't navigate an online transaction. If it were me, I would be more concerned about giving you, an individual, instead of the company, the credit card numbers. I would think it would be much easier just to walk them through the process.
"This is basically a backup plan in case I encounter someone who's queasy about putting their credit card info on my laptop ..."
I have been here for over 10 years, with several thousand sales and thousands more on other platforms. This has never come up for me.
I really do think you may be overthinking it.