I agree that clubs would find a way of fucking it up but there's plenty they could do. Live music, bars, varied food stalls (not just the big standard pie & bovril), funfair rides, small sided games for the kids on the pitch due to the better weather.
I get your point about space but Clubs could tie up withe the local council to have adjacent streets closed off to traffic for the day just like they do for street markets or the like. Clubs like St Johnstone would have no such issues!
It would be possible but I share your pessimism in their ability to make a success of it. They'd do it half arsed and fail miserably.