Too much to read, so not sure if anybody else said something similar:
I think the MTL tanks that are out there already have exhausted the possibilities for anything new/improved/different. The nautilus is just about the best thing with prefab coils. The Kayfun is hard to beat for a rebuildable. @AndriaD is always touting the Achilles for a MTL dripper. Outside of that, I don't think there is much room for improvement. You can only do so much with a tank designed to make a single mouthful of smoke at a time. Plus, the money is in cloud chasing. Everybody wants to grab a mod and chuck clouds these days.
I love my Achilles!!!!
Tight-draw, MtL;
AMAZING TH, allowing lower nicotine level without "weakening" the vape;
Top-fill, no "vacuum" issues since it's an RDA;
Holds 2.5ml;
NEVER leaks;
Titanium, so VERY light;
Builds just like a Kayfun (easy peasy!).
It's pretty much cured me of tanks.
Andria