You don't have to watch me browse the results of the 'find' menu, for example, you just need to know what the options mean for when you search your world.
It certainly would have been nice, and saved me many, many hours, if any other tutorial series' had looked at more than 'aquifer, flux, and metals' when using the <f>ind options on embark. Heck, I wasn't aware that there was ANY reason whatsoever to allow an aquifer, until I first watched Andrakon's SPC series. Now, I search FOR aquifers, instead of avoiding them.
When I was a total noob, it never occurred to me that temperature, elevation, or even hitting <Tab> and the <F1, F2. . . > keys were an important part of choosing an embark. This is definitely a place where you can easily improve on what's already existent on YT. The number of vicarious facepalms I go through, watching 'tutorial' videos, these days....
It depends on how you use it... which may mean a tutorial in itself.
True; the same can be said for the in-game UI as well. The difference being that there are already plenty of tutorials that use DT; there aren't, however, (m)any that don't. A tutorial on the in-game controls would probably be more useful to Mac and Linux players, as well - AFAIK, DT is iffy at best on non-windows platforms.
Machinery, as well, is rarely touched on in tutorial videos (beyond 'here's how to hook up an atomsmasher bridge' that is). A great niche that needs filling is the application of machinery to non-defense tasks. How does one, really, set up a proper pumpstack? The most recent video I've seen on that was from DF2010, and poorly-made at that (as far as production, not content). How exactly does an impulse ramp work, and what's the advantage? You are, after all, a proven expert on that particular topic.
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Basically, with the caveat that I personally will support whatever DF content is spread around (even the downright awful vids I've seen!), I humbly suggest you play to your strengths: there are already plenty of basic tutorials; there are few (if any) that cover the sorts of topics you've expounded on in these very fora. Remembering the the past year or so of play, it wasn't until I started watching non-tutorial videos that I personally even realized just how deep the rabbit hole goes; seeing a successful minecart shotgun does a lot more to motivate a player like me to learn the basics than yet another 'here's how to build a farm plot' video.
But, once again, you know your subs and your interests better than I ever will.