What if they use the number of entrants qualified for 2020 Worlds but the country can send whomever they want. Nothing is going to be completely fair but this seems reasonable to me. So, the US qualified 2 pairs for 2020 so they can choose any two US pairs, which means K/F can go. But if youR country didn’t qualify in 2020, you don’t get a spot. That would keep the field the same as it was supposed to be last year while avoiding tech minimums.
All ISU member federations are entitled to 1 spot per discipline at Worlds IF they have a skater (or team) who has achieved the minimum score to fill that spot.
There is no "number of entrants" qualified for 2020 Worlds by country. The countries that had skaters on the entry lists were the ones who had skaters with minimum scores to fill the slots that the country is entitled to by virtue of being an ISU member.
Worlds is not like Olympics where the total number of entries is capped by number in advance.
So that doesn't really solve the problem.
You could say "All federations who had a skater on the entry list for 2020 Worlds are entitled to send that skater or a different skater, and all federations who did not have an entrant may not send anyone."
But that would mean that a federation who had exactly one skater who had the minimum scores for last year's Worlds but who has since retired or is currently injured could send their best skater this year who might be very far from being able to achieve the minimum.
Or a federation whose one strong skater was injured last year and therefore not on the entry list might be recovered now (and might even still have valid minimum scores earned before the injury). But since there was no other skater with minimums to fill that slot last year, should a strong and qualified skater be kept out this year?
Or a federation's strongest skater(s) were competing as a junior last year and are now ready (or required by age) to skate senior this year. There was no one with senior minimums to be entered in the list last year but there are skaters strong enough to earn them this year, if there were any place to do so.
For federations with few skaters who can earn the minimums easily, or with several skaters who can each earn them only on a good day, whether they have at least one in a given discipline who has valid senior minimums and is healthy enough to compete at Worlds will be quite changeable from year to year.
But the ISU rules entitle each federation to one spot at Worlds each year assuming they have someone to fill it.
It doesn't seem to make much sense to take that right away from some federations based on which federations were able to fill their entitled slots a year ago. Especially if you will allow federations who do not have a skater capable of meeting the requirements to fill a slot just because they did have a different skater capable of it last year.