Actually, that might be the best solution (not the stupid one I have yesterday).A non binding referendum between “No deal” and “No Brexit” would be sensible. With the acknowledgement that parliament is still to try to get a satisfactory deal, but that they understand what the “default position” should be if an acceptable deal is not agreed upon.
Set the referendum between "no deal" and "no Brexit".
Let May continue discuss with EU for the remaining two months. At the end of it, she sets another vote in the parliament where the parliament decides if they accept May's deal (which might be better than what they have now, or not). If the parliament decides to accept it, then soft Brexit. Otherwise, the result of the referendum.
Or do the voting first, and the referendum later (something like the voting at end of February), and the referendum at end of March (while there is still time to revoke A50). Of course, if the parliament accepts May's deal, no reason for referendum.