The whole thing is a poisoned chalice.
Corbyn and the SNP will vote against everything just to try and force another election, the house of lords will reject anything just to stay in the eu and the eu will reject any proposal knowing they can turn this "transition" period into an indefinite state of vassalage till a pro-eu government is elected an goes back begging for -re-entry nd we'll lose all our ol opt outs an get forced to sign up to shengen and the euro.