There are no perfect solutions in this, just least worst ones, although promoting as is, and not relegating teams and increasing the league sizes all the way up the pyramid (albeit temporarily) seems as good a suggestion I've heard so far.
Either they attempt to complete the season or they write it off. Any fudges would, as you rightly say, result in legal challenges which in all probability drag on in to the following season and might even result in the House of Lords ruling that promotion and relegation can only be decided over the course of a full season, in that case how would you undo the 'special rule' you'd implemented part way through a season.
Agree. Sadly I think they will complete the season - no matter how long it takes. It will be a bit of a farce but then, as others have said, best 'worst option'.
I don’t think this season will completed and even worse I have my doubts as to whether the new season will start anytime this year.