I believe that the only solution is to finish the 2019/20 season regardless of how long it takes. With more or less 9 games left to play, this could realisticly be done in 6 weeks: ie 3 games to be played every 14 days until its conclusion. The same could/should apply to the lower leagues, too.
If a playing window of the said 6 weeks can commence when deemed 'safe', then possibly May to August could be the right time. On completion, have 2-3 week 'off season', with busy bods arranging the new fixtures for all leagues and players leaving and joining new clubs.
The 2020/21 season, for one season only, would be played WITHOUT competing in the League and FA Cups, thus helping for an early end to the season, giving players and countries time to prepare for a delayed Euro '20 in the summer of 2021.
Easy, or what do you all think? 😃