That is all technically possible to do, but not currently because of the way how this currently works in the backend. I will look into it once Im finished with what Im working on right now with regards to the template, no-one has ever asked for an API because they usually could use one of the options already available.
jachym,
please have some discussion before you publish an http(s) interface for pushing data into meteotemplate. propose an api syntax on wxforum - i guarantee you'll learn a lot.
many, many people have done these already. some of them are really good. some of them are complete rubbish.
as soon as you publish the interface, you have to support it, and deal with backward compatibility. this is not something that you want to change. nor is there any reason to iterate on an interface - we already have many years of experience and existence proofs of both good and bad.
you *could* use the WU interface; make meteotemplate accept data in WU format. that has the advantage that you could simply point any device that 'speaks' WU directly to meteotemplate, and it will just work (e.g., the fine offset observers, the acurite gateways, etc). the only question is whether the WU api provides all of the data you need for meteotemplate.
i'm not saying the WU api is an example of a good api - in fact, it is not. but it is well known, supported by many devices/software, and well understood, even if the behavior of the servers that sit behind it are not
meanwhile, if you could clarify the behavior of the http/get interface that meteobridge uses, i can make weewx work with that, then transparently (to the user) transition to the new api when you figure it out.
m