Basically it shifts risk to developers and we want developers to install lots of green energy over the next decade.
(I just noticed the recommended related article is research on exactly this topic)
There's other machanisms to incentivize demand closer to production, though whether they are being used optimally is debatable.
I would say that improving transmission seems like a much better solution but again I think zonal pricing can help there as it could then be more easily sold to the public as being able to import the cheaper (say) Scottish energy to your local zone, whereas at the moment there's no apparent direct cost associated with blocking pylon projects forever.
Yes, and if you are an individual, family, or even the vast majority of businesses you aren't going to move to Scotland over this, you are going to pay, no choice. So effectively this would have increased bills for most people, so bad politically, with only a marginal change to demand.