Was at Mondial de la Bière in Montréal last year, which was kind of run along those lines.
The 125ml was ok. Just ok. They'd a huge amount of stronger Belgian-style beers on offer, so get why they were using the 125ml glasses.
Personally though, I found it pretty annoying having such a small glass. A 4.5% red ale is gone in two or three gulps. IMO, that's not really enough liquid to taste and enjoy the beer properly.
Would point out though, queues were minimal and it wasn't an all-you-can-drink event. Coupons cost CA$1 (€0.70), with beers costing between two and six coupons each. €40 would probably be a decent enough price to go on here. Though people will make it their business to get their money's worth out of it.
Beer festivals, for me, aren't just about trying as many beers as possible, they're about sampling beers, getting a half pint of what you like and spending a good few minutes actually drinking that half pint.
Also, there's zero chance I'd be interested in any festival that involves frequent queueing.
Problem will be getting the guards approval. They would look at it as binge drinking. I tired to do that here 10 years ago and was stopped . I know that's along time ago but several night clubs were forced stop the practice . It's a great idea but I think we are a long way off it in the minds of the powers
Sounds like an interesting idea. The things that would affect my decision to go or not would be the list of beers available, whether bottle or draft and the tiny glass, not a fan. I enjoy siting down with a beer, savouring it a bit and having a chat, can't imagine you'd be doing that with a 125ml glass. Probably queueing all day.