There would be hell to pay if they tried - it would need the council to approve change-of-use which would go down like a lead balloon.
The real risk is that someone proposes putting up just another glass and steel box, gets turned down, and we’re left with a blackened hole in the ground for 10 years surrounded by wooden fencing with grotty fly-posters all over it.
The architecture there is all mid-19th century, built in local yellow sandstone. Union Corner was a grade B listed building which is about as high as you go without being a castle or national trust monument.
This was how it used to look:
