howabout That would be a pointless approach, because at least within the 2 year A50, there is no time for a special deal, just 2 possible ones:
It is either WTO, or EEA /EFTA with ECJ & FOM - the negotiating would be to keep the same access for services
The Uk is legally obliged to pay the agreed contributions until Brexit happens. so at least until end March 2019
Otherwise, the UK would be taken to court and have fines to pay in addition.
After Brexit, of course the UK and refuse to pay anything and go the Patrick Minford route of no tariffs on any goods from any country - under WTO rules, the EU & UK must treat each other the same as the other 170 or somcountries in the world.
At risk for the E27 are up to 12% of their exports; the UK up to 45% of goods exported PLUS all the services, since these are not handled by WTO.
Some countries - e.g. Canada - may agree to a trade deal to come into effect the day after Brexit, on cut & paste basis of their current EU deal.
Many won't, so that means 5-10 years for new trade deals - or lomger, since the UK hasn't the negotiators to handle several in parallel.
"Guarantee right of return to UK citizens living in EU"
I may have misunderstood what you mean here. All UK citizens anywhere have automatic right of return to the UK.
It would be against international law for a country to prevent its own citizens returning 