The move that makes most sense is to call the domestic league season as it is now on a PPG basis but with no relegation. Teams in automatic promotions spots on PPG move up the ladder. This means the pyramid is going to look different for a couple of seasons at least but that is easy to cope with and can make the decision, if wanted, to readjust if/once a vaccine is found.
The League Cup can be sacrificed. PL teams won't miss it and I am sure EFL clubs would gladly take that loss too if it aided getting things going sooner. I suspect once gone nobody would miss it and it can stay gone.
FA Cup remains but replays are no more.
This will mean the 20/21 season can get started BCD as soon as is possible which would give the best chance of being back on schedule come next summer with another lockdown seemingly inevitable between now and then.
This leaves a decision to be taken on whether they want to play out the 19/20 FA Cup in the early part of the 20/21 season or simply call it null and void. I suspect with so few teams involved they may want to play it out but either seems fine.
I think this is a logical and attainable solution for the domestic season for England and indeed across Europe with the majority of "losers" in this scenario only really losing out on a potential end of season promotion via playoffs where the individual probability of success for each club is not large enough for them to feel overly aggrieved.
The Champions and Europa League are more difficult and complex to resolve. The 19/20 EL can probably be declared null and void with zero last 16 second legs played and two last 16 first legs not played but the biggest factor in deciphering the importance, or rather non-importance, of it being completed in comparison to the Champions League being the disparity in terms of money involved. The CL could be played out in the same way as suggested for the FA Cup with the 19/20 season being completed during the early stages of the 20/21 domestic seasons or could also be null and voided. I wonder if the profile of the clubs already qualified for the quarter finals (PSG, Atalanta, Atletico Madrd and RB Leipzig) could impact on the likelihood of the 19/20 season being declared null and void? I'd certainly suggest it would be more likely to be forced through were it Real Madrid, Barcelona, Bayern Munich and Liverpool who were already booked in. In any case I am not sure of the viability of any Champions League or Europa League while the pandemic is ongoing sans vaccine with it just being a logistical nightmare with every country across Europe likely to remain in differing degrees of restrictions for the foreseeable. I could see a scenario where we have no CL or EL for the next 18 months and it leads to a European Super League being accelerated enough that that is what we return to when we next see football on a European basis.
In any case, domestic football is the key and more easily resolved/adjusted and I think the above is by far the way to go.