The EU has no intentions forcing the UK to do anything at all. They can leave without a treaty if they chose to.
The EU Agenda is the only one that makes sense.
...which has never been defined since no one has previously left the EU, so un-chartered waters, look at the cost of the "divorce bill" it changes depending on who is speaking.
There is no point discussing the status of UK citizens in EU countries before both sides know who will pay for their respective health insurance, retirement and all those thing.
There is no point discussing in how far the UK will participate in EU research programs, before it has been sattled how much they are going to contribute towards them and in how far they keep their commitments for ongoing programs.......
I suspect it will be like the rest of the world who have expats living and working in their countries, if bought in by a business, that business and the individual negotiate a contract on taxes, benefits etc etc etc., if the individual retires, they meet the criteria of the host country, this is common the world over and nothing new. In the Bahamas we have lot's of expat's both as workers and retiree's with no problem.
As for research, foreign countries provide grants to each others research institutions or universities on a regular basis, also nothing new.
I think I may be missing the issue that for most Europeans in the EU, national countries and how they work with each other has been dying away, as I have never been in the EU I am used to country to country dealings and in some respects, cannot understand the difficulties. Most countries in the world do not and have not had a EU type arrangement.
Nope, they will just be back to WTO tariffs and UK citizens living in the EU would be illegal.
...which the EU is trying to avoid since all their citizens in the UK will also be illegal, both sides have the same issue.
you got that 180° degree wrong. The EU is very clear on the principles, those that the UK formed and agreed to, but those give the UK options. The UK side comes with demands.... a car dealership is not "demanding" money from you, they give you options to buy. You can always walk away without buying.
The UK had demands as a member and they were rejected as expected, so they took the next option which was to leave.
Now they are in negotiations for what they would like, but as the member who is leaving a continuing union, they can only request additional benefits, not demand them, they have no authority to demand. I do not think the EU will be "selling" any of their principles as it would affect the other members of the continuing body, they can however, demand that the UK meet certain criteria to gain access to benefits of the union.