As you have an extended residence, I'm sure the property itself is worth salvaging the structure, as the size would be worth working with. I would have a pro quote to remove it all, and also quote to re plaster. Factor in the cost of painting, possible re wiring, trimming as in skirts and architraves, then consider your time and inconvenience to temporarily vacate. It's sounds much worse than it is. Asbestos is pure evil, and unfortunately so many people hit this hurdle and the only way out is to bite the bullet. So to speak. I hope it works out for you.

They're supposed to check first!! If they suspect asbestos then they shouldn't be touching it. 1 - 2 foot hole? Was this asbestos in the wall cavity or where they cut the holes? That would be a lot of dust even from a plaster wall..... They may not care about their health but what about yours, family, etc.... I'd be looking into this further. Dept of Fair Trading may be your next phone call........ Keep us posted.

a freestanding post can be supported from the roof, floor, corner post and railings without needing to be attached to the wall...a good handyperson should be able to advise on specifics and you may also like to consider a more expensive but longer lasting steel frame structure by consulting a metal fabricator

I’m struggling to understand why the pantry was installed there. Was there no room to have a shallow wall pantry with hinged doors? Anyway, the suggestions you have made I think are a good compromise. Putting a false panel above the door, attached to wall not door, and the shelving. But if you have room for shelving I would think you would have had room for a shallow wall pantry?