The current guidance from DCMS (and I stress current because it may all change by April) says no "away" fans admitted. Mainly to cut down on lengthy travel. They don't want people travelling about the country and spreading CV19. If you live in a tier 3 area you are strongly advised not travel outside it. So if, say, Basildon is tier 3 but Chelmsford is tier 2 members resident in Basildon would be discouraged from attending the county ground. I know the current tiering system hasn't been applied at district/borough level (although some Tory backbenchers are pressing for just that) so just an example.
Clearly all the ground would have to be used. The very narrow walkway around the back of the public side must be a real headache. You'd have to have a one way system? My guess is you could get around 900 people in if you have to have 2 metre spacing. I don't know if the club have commented on how many they could accommodate.
Someone asked about using outgrounds but that was quickly shot down on cost grounds. The funny thing is if you told people to bring their own chairs and sit in household groups only it would probably work quite well at somewhere like Castle Park....