I disagree with using Euros and 4C's as qualifying events for Worlds. For one thing, every 4C nation gets three entries (still) to 4C's, giving that nation multiple shots to qualify skaters for Worlds; Euros are limited by prior year placements. Besides that, I think that it is legitimate to give ailing champions the ability to skip Euros to be healthy for Worlds -- it's not the playoffs, just another competition -- and/or the Federations to use it to determine their own spots, and that doesn't always include their gold and/or silver medalists.
I don't think that skaters should be in championships unless they show that they've been able to meet the minimum requirements for a SP in some combination of international competition. For example, I don't think that a skater who has never done a 3/2 and a triple of out of steps should be at a senior championship.
I also don't think a minimum score should be required from anyone who has qualified for a championship FS (and can do the minimum SP requirements).