A (Baron) Unilateral exit from backstop
B (Baron) No deal exit in the absence of a withdrawal agreement
I'm already punting that Bercow refuses both of those because they're daft.
C: (Clarke) Customes union
D: (Boles) Common market 2.0
E: (Kyle) Confirmatory referendum
F: (Jones) Referendum before allowing no deal exit
G: (Cable) Parliamentary supremacy
H: (Eustice) EFTA / EEA
G is mere political exhibitionism
So that leaves us E and F as the only plausible options, both of which ask for a confirmatory referendum, and the Kyle amendment with most credibility.
The Brexiteers will probably quit before accepting that policy, and the government will collapse.
A referendum, a leadership election, a general election.
Let's go large and have all three.