I'll have one more go at trying to explain why the EU27/Commission cannot and will not try to impose additional conditions on revoking Art50......
As there is nothing written in A50 regarding revocation after it has been invoked, the whole issue is wide open to interpretation and we are interpreting the situation very differently.
You take the view that the EU will rigidly stick to it's own laws and rules and will not deviate. If it's not explicitly written down allowing something to happen, it cannot. I take the view that the EU will cynically manipulate a situation to suit it's own ends, especially where nothing is written to prevent it taking a particular course.
Take the current 'negotiations', A50 says that the Withdrawal Agreement must take account of a framework for future relations and yet the EU thus far have pretty much refused to discuss the future, so they are not even adhering to A50 properly.
The phased negotiation that the EU has insisted on is absurd as everything is interlinked. How can you decide what will happen at the borders when you havn't discussed the terms of trade?
The reason that they are not adhering to A50 properly is because it suits them.
This whole discussion is hypothetical anyway as the government won't try to revoke A50, but I'll leave the last word to this Guy.
“If Britain changes its mind, it would find an open door. But like Alice in Wonderland, not all the doors are the same. It will be a brand new door, to a new Europe, a Europe without rebates, without complexity, with real powers and with unity.” Guy Verhofstadt MEP and BREXIT Negotiator for the EU Parliament.
https://www.politico.eu/article/guy-verhofstadt-brexit-european-parliament-to-uk-you-can-stay-in-eu-but-lose-perks/