There is a series of guitar instructionals that, in my opinion, are outstanding. But I have never seen the format used by these books elsewhere. Here is why I found the material outstanding -
1. Tunes are commonly played.
2. 3 Versions of each tune - beginner, intermediate, advanced.
3. Recordings for all material in the books.
4. Before each tune is played, the author narratives how difficult material should be played.
If someone produced material for tunes using this format, it would be my "go to" site to fiddle notation.
fiddlevideo.com does that but it is a website and you have to subscribe for all the versions. They do have quite a few very good free videos and the teachers are all excellent and some of the best in their genres.
I offer a bunch of Cajun tunes broken down at 3 different levels, just not for each song. I like that idea but really, some tunes are just harder or easier than others. Think of show-off tunes like the Perrodin two-step as opposed to row your boat. One can be fluffed up but the other can only be made so simple. Then there's learning by ear (a Cajun tradition) which shouldn't require any tablature or notation but does act as a handy tool for beginners or to help kick off a tune you've previously learned. Points to ponder...
'78 RPM record collection' 49 min
'bow quality/descriptions' 11 hrs
'Tuning for The Cuckoo?' 1 day
'Royce Burt violin #489' 1 day
'Never a dull moment.' 1 day