It's totally possible, but that sounds like it would cost a lot of development time. The KeePassXC project in particular decided not to implement cloud connectors due to a lack of resources.
I'm not sure why you think this is that difficult of a task. This is standard fare for how clients integrate with a service. There's how many third party Twitter and Reddit clients out there, plenty made by a single person that just communicates with a public API made for integration. You can spin up a Discord bot in a few minutes. Why is this any different for syncing a file over an API?
