In conclusion: avoid humiliating others
The UK is in a weak position because a "Hard Brexit", its alternative to a negotiated deal (its MESORE, would be a disaster. Trying to punish them would be counter-productive because, in any case, they will remain partners and this future relationship has yet to be defined. In negotiation, you don't want the other party to feel humiliated or brought to its knees. That's why it's wise to remember the old French saying that I quote regularly: " Never wedge a cat into a corner without leaving a cat flap. Otherwise, it will turn around and jump out at you." .
As long as there is a need to adhere to the solution proposed by the EU, the other party should be offered a choice that is as painless as possible. No, it's not their problem, because it's a common problem and we need to solve it together. To succeed, satisfaction must be shared. Let's hope that this postponement will make it possible to find the right arrangement.