I think Baz is right, the common sense approach is to postpone for a month or two and then take stock of the situation at that point. It might be that by then the worst of it is over, much like things seem to be on the wane in China, or we might be experiencing the worst of it by then, who knows. Either way, I think the Euros will be postponed until 2021, which will give the club competitions a chance to finish if things have improved. They'll still have to cram things in like crazy, playing at least two games per week, and I wouldn't be surprised if they cancel the FA Cup this season to give the PL and CL a chance to conclude.
I've no idea what they'll do if they don't manage to finish the games by about July/August. The players will still need some sort of break in the summer before next season starts, and whatever approach they take there are going to be teams and fans that are annoyed. If they void this season then Liverpool and their fans will be livid, as will all the teams chasing promotion in each league, but if they just call things based on current league positions then that disadvantages teams who had a nice run-in and gives an unfair advantage to those teams who had a horrible run of fixtures to end the season. Playoffs for relegation and European places have the same problem.