Why would the EU offer an EASA membership for a third country that just destroyed a peace treaty they have signed, does not fulfill its past obligations and seriously disrupts EU commerce? Answer: It wouldn't. Easy as that. The EU has already done its homework with its unilateral no deal legislation that it can withdraw without prior notice at any time, just protecting its own interests. And Airlines, workers, shareholders in a third country are not an interest to the EU.
Whilst I think you are right, I guess we all know that the owner of the UK and the EU (big business) will make it clear to their respective Governments that they have to work something out.
BTW, there is a training company in the UK just changing all their licenses to the Austrian authority - whilst staying on their premises close to London.