Just daydreaming:
I was thinking that the team could award tickets to season ticket holders, with 25% (one of every 4) of the seats situated on a social-spacing basis.
Season seat holders who didn't like the arrangement would have the right to give up their seats without losing long-term rights to seats in the future.
25% is better than none, teams could retain 25% of their gross and there would be at least 25% of the crowd noise.
On a more radical and futuristic note - there must be a way to utilize Skype, Zoom etc. to transmit crowd reactions from home computers to a centralized "crowd noise collector."