I don’t think it’s far fetched at all, it makes a lot of sense to want to keep track of exactly what you have and haven’t seen.
It’s been discussed if we should add every single performance as an event for this purpose. Logically this would make a lot of sense and it would allow you to select exactly all the performances you’ve seen. But practically it would be a ton of work, splitting festival into it’s different stages or venues is already quite a bit of work. This is currently not in the event style guide, which only mentions splitting festivals into days and venues.
A potential solution would be to not force but allow people to split the performances as separate events where they have a personal need for it. This doesn’t seem ideal because we would be storing data in 2 different ways, but it’s a solution that doesn’t need any code change so perhaps it could be an option until we come up with something better?
Another temporary solution, that requires less effort, is to edit your collection of events and put the missing info (exactly which performances you’ve seen) as text in the description field. Visually not the most pleasing solution, but you could just store it there waiting for future updates.