Stock email reminder.

2 clicks to open a case.

Ditto to close it.

One click to relist.

Something in the order of 60 seconds total elapsed time over a week and a bit.

Set your blocks properly and the frequency of NPBs will probably reduce.

Apart from anything else how are you going to enforce fines? There is no requirement for a buyer only to provide any financial information to eBay, and as they are not purchasing anything from eBay AG, I suspect such a requirement would be illegal.

Or do you think all new members should have to make a (possibly) non-refundable deposit in order to use the site? That, I suspect, will ensure you don't get too many NPBs. You probably won't sell much to the decreasing number of buyers, either. There are already plenty of sites with sellers but not many buyers; I don't think we need any more.