The seller's terms can never override the terms and conditions set by eBay,
None paying bidders can be dealt with by the proper channels through eBay, so the seller does not get an NPS strike. For an NPS complaint the bidder must prove he has paid.
It is a real shame to block zero feedback bidders - some bidders register just to buy one particular item and at this time of year many established eBayers register a new id so their family and friends can't see what they've been buying for Christmas presents.
I love my newbies. I have had a few problems with newbies, but I've had a few problems with powersellers who have bought from me,
A non-paying bidder is an inconvenience, not a disaster.