I would reconsider using Elysia. I was also very excited by it and I thought it would be great but it has got errors and issues with different library versions and things like that. Also the whole Eden thing doesn't work for me for whatever reason. I have a monorepo. Typescript keeps complaining. Also if everything is defined in a single file, then it works well. If it's in different files, it breaks the whole type side of things.
Huh? It works fine across different modules. It helps to read the documentation thoroughly. I don't mean that to sound snarky, but it's likely you missed something if you're not able to modularize your route types.