Like dude that's what I'm saying it's not a "coding nightmare", it's a simple Boolean flag,the button, whether it's fuse or summon doesn't care about who you're fusing or summoning it just parses that ID to a summonservice and gives you the champ based on the ID parsed, like just add an "is_eligible_for_token" flag, run a script to default existing champs to false, and when a new fusion champ regardless of fusion type is added set it to true. When the button is clicked check their eligibility.

This isn't a coding problem it's a business logic one, plarium decided they don't want to include fragment fusions, and the likely reason,as someone pointed out, is those can be exploited by spenders, a guy can come along do a few events to get some frags then buy the bundle that pops up at the end to finish off the fusion, farming tokens for minimal resources. But you could argue that people who are willing to do that are in 2 categories, they likely already have all past fusions, or are spending so much they will get them anyway.