I agree with you, but the big problem I see with a hard-line Brexiteer coming in is would they be zealous enough to ride roughshod over international treaty obligations and actually go for a no deal at the end of March? (A no deal, no deal, not an imaginary 'managed' no deal with a transition...
A hard-line Brexiteer coming in would require an Article 50 extension and a delay to Brexit to attempt that and isn't going to going to get any alterations to the withdrawal agreement anyway.