I am discussing a possible instructional presentation with an established entity, but they are specialized in guitar. Now, I was wondering, if you were consulting an instructional package (video + pdf) that focused on scales and their application across the neck, what sort of bass would you prefer the material demonstrated on?
I've honestly never gotten much out of videos, unless it's extremely finger technique specific. It's usually too hard to see what the fingers are doing, and I'm not sure it's ever necessary to see them. Maybe for slap, you kinda need videos since finger technique is so critical to the sound.
Anyway, my thought is that if you clearly write out the exercises and present them at various tempos, I think that is enough. But a hybrid video and audio format might work. Maybe just a few videos here and there. I really dunno if a scale book needs video.
I know in the Gary Willis book, I do sometimes wish he had some video, (in one or two cases) just to outline an exercise, but once you get the fingering, an audio file that you can loop for hours if need be is helpful to really get the exercise in your hands and head. Looping video to hit on a downbeat is a dicey proposition and is also super annoying to watch.
Concerning which instrument to use, I voted all of the above, also like the Willis book, but that could be pretty time consuming. if you do it on 6 string you can cover all the basses (pun in tended) and inform the 4 string players to just ignore the B and C string areas. I think 4 stringers need to put more effort into understanding the relationship between 4,5 and 6 strings anyway. They seem to act like it's some kinda mystery.
One advantage of a 4 string presentation is that it takes a lot of shifting to get up the neck and that's probably something all bassist need to work on. But of course you can shift on any bass...
Just my 2 cents...