An experienced user may use a different upload form, as long as the image ends up with the appropriate template.

At least, that's what I have always done where i am involved:

- Let the rules say that the images must use a free license such as X, Y, Z... but explicitly allow any license accepted in Commons.

- Suggest using the WLM upload campaign, but document that they may use a different as ong as they use {{Wiki Loves Monuments 2019|country-code}}.

- Put the burden on the uploader to ensure that they are using the right identifier but otherwise allow that it gets fixed by someone else.

By focusing the rules on the result instead of the how we avoid needing to verify how it was done, and only the final result is needed. It also allows advanced users to use other means, such as uploading using Commonist.