Funnily enough, I've been toying with the idea recently but please don't read too much in that.
The LGBS has gone and while it's been rebranded as the UK Bass Guitar Show in Manchester, many were disappointed at the 2020 show. Stevie Williams stopped organising the UK Bass Show to focus on other things. I hope he won't mind me mentioning this but many years ago he told me that that if he broke even on a show, he considered it a success.
So while there seems to be a gap in the market, it's fraught with financial risk for the organisers. it involves a lot of work from a team of people and up front financial investment in booking venues, promoting and securing (often paid) artists to provide assurance of value for money to everyone. And that's pre COVID. Post COVID, the industry has been squeezed generally. Unlike the US, turnover is down and promotional budgets within the industry are tighter.
I was looking into exhibiting at a London construction show a few months ago and faced the prospect of being charged 75 quid for a plate of sandwiches if I wanted to buy food on site. Then there are the mandatory PL insurances, health and safety risk assessments, the cost of storing kit away from the stand etc. etc. It was like being nailed to the wall and slowly drained of outrageous amounts of money. But the construction industry is a bit bigger than the musical instrument industry.
So while its possible, I think a lot depends on finding the right venue. Maybe somewhere in the non-for-profit sector like a school, charity or trust.