Hey, it sounds like a rather simple implementation. A long list of custom capabilities and a device driver that retrieves the info and compares them with a cached object to detect changes. Trigger flow cards when change is detected.
But like everything its hard to make it without an actual device. I am just finishing my new EV charger app and learned it/wrote it in 4 nights.
I like the concept though, adding more type of controllers to the mix. For example if Fibaro home controller would be an app through the API I would get one just to make sure all my Fibaro devices get firmware updates etc. Having homey as the grant orchestrator.
What you need to do is wrote functions in nodejs that get info from the api. If you succeed with that, than following the getting started tutorials, look at the capabilities concepts and how to trigger flows. Once you have that clear its about creating the device class that links these elements together, one device per functional element you want to implement from the API.
But I do feel that a device is not a very flexible thing, so you need to decide what each device should do and build it for that purpose.
I hope it helps a bit, it is not hard. I do not own a Homepilot, so I can not help out.