The idea/hope is that MS governments will be more willing to give in to British demands. I think this is a flawed argument that overlooks the dynamics of politicization.
1) when Brexit 'hits home': domestic GDP growth damage, jobs lost, rights lost. The harder Brexit, the stronger this effect, with No Deal as extreme.
1. The UK is leaving against our wishes (any damage is the UK's fault).
2. We have offered several options (the UK must chose one of them).
3. All these options are reasonable and logical (others are not).