I'd argue the opposite: if the EU shows that it isn't willing to give any special deals (other than "regular" EEA or EEA-like membership, which is what matters

I'd argue the opposite: if the EU shows that it isn't willing to give any special deals (other than "regular" EEA or EEA-like membership, which is what matters really) to any absconding members, any other members seeing how bad it went for the UK having to stand alone would think twice before attempting any similar action. Regardless, you seem to be implying that the UK should have their cake and eat it too (I dislike that expression, I apologize). As the larger market the EU has a lot more power in negotiations, it's the downside of standing alone; if the UK want to get something significant out of the negotiations, they're going to have to give something significant back.