I like the idea and wrote a longer comment. But I must object to your two universal statements as they are without further qualification I find them false.
It is possible to start any program via a file association even if it does nothing with the file that the action was activated on.
Saving a new file only requires the file chooser if the application was started first. If the file is created in Explorer via the New ... Templates and then opened the use of the file chooser can be avoided.
It's too bad Templates got flooded with junk back in the Windows 95 days and so people stopped using and Developers stopped creating Templates. OS/2's heartier version of Templates, I recall being extremely useful. Windows' Templates seem derelict and forgotten ruins of the ancients in Windows today.
Isn't a template just an empty document/file/archive stored in a specific folder somewhere? That doesn't require and special technical knowledge or anything, just save an empty file there.
I have a dozen or so software shortcuts (notepad++, cmd, etc) in the SendTo folder, which works similarly.
The issue is that it is a small tragedy of the commons. The more apps put templates in the Templates folder the longer that context menu gets and the harder it is use. Context menus have never been a great place for lists of options that might grow unbounded over time. In the early years of Windows 9x you could directly watch that: almost every application installed a Template because it was a new thing to do and Windows encouraged it, then users started complaining they had too many items in that menu and it was too slow and they stopped using it (or never bothered learning it in the first place), then all of the applications stopped installing templates.
(The SendTo folder had a similar wave of too many then too few applications installing to it. I feel like every application that really made sense on the context menu seem to have moved to direct context menu entries in the main context menu rather than SendTo.)
It is possible to start any program via a file association even if it does nothing with the file that the action was activated on.
Saving a new file only requires the file chooser if the application was started first. If the file is created in Explorer via the New ... Templates and then opened the use of the file chooser can be avoided.