This *may* be shifting, partly as Corbyn wants to "rule out No Deal" while being sceptical of referendum/remain. And partly as Boles-Letwin-Cooper might have a mechanism to do it.
Corbyn appears to be demanding/supporting this (while cool on & opposing a referendum, and thinking Brexit deal needed)
* advise PM to request extension to 29/4 (or 29/6 if derogation solution)
* if no deal/extension by (29/3, 29/4 or 29/6) instruction to revoke by 5pm that day (!)
* commitment to seek majority for deal, starting from current WA
This could kill this idea (though that means No Deal remains default)
If could be clear there is majority for content of Withdrawal Agreement (200 Cons + 150 Lab), subject to content of PD & agreed process of parliament role in round2
(Nb, backstop is *not* crucial dealbreaker for *this* majority coalition)
(Nor does it wreck negotiating hand, if WA negotiations have closed, though that would be one critique).
Govt could offer to seek the short A50 extension instead. (It is a final breathing space, not a solution).
* embark on a citizens process on what next, with no options ruled in or out
* hold referendum to ratify revoke
* hold a general election
(Can't bind successors)
* if Commons has not voted for a deal (by eg 1st March), the govt will seek an extension to 29/5 or 29/6.
* leave revoke out of it (but suggest have in back pocket if March)
* think Gvt cd accept with talks on deal
* it is current legal text
* negotiation on political declaration is contentful part
* process for Commons engagement in future negotiation
+ Agree to hold a Commons free vote on referendum (& Euro elections too): rule out referendum if this loses.