Derivation_url: allow adding an URL "file extension"

For now, derivation_url if generated ending with the file obejct serialized.
This makes a long URL fore sure, but it works.
When using some CDN solution like Cloudflare, only some “file extensions” are being cached, otherwise we have to define a specific Page Rule to force caching of some URLs.
I’d like to have URLs generated with a pseudo-file-extension ending, based on the file’s content-type, which would look more natural to users and to Cloudflare, too.
Any idea ?

Thank you !