^there's sort-of a thing like that out now. the clearomizers/smokymizers are nothing but a tank themselves, with a wicking material that carries the juice up to the coil (in these, the heating coil is at the top of the clearomizer, and the clearomizer tube itself serves as a tank you fill up, and can visually check your liquid level). I haven't had any luck with the "new improved plastic" kind; i always get a plastic-y burnt taste from them (using 70/30 pg/vg). The old style regular clearomizers wicked my 50/50 juice just fine, but they always leak where the tube connects to the base. Just my experience, YMMV.
I like the carto-tank better, because it still gives you that visual indicator of how much juice you've got, and also the coil itself is surrounded by saturated batting, so no dry hits/burnt taste in my experience. You can buy pre-punched/slotted cartos for a premium, or if you're handy you can punch your own with hammer and nail, or slot them with a dremel.
I think one of the reasons i love carto tanks so much, is I can never tell when to fill my carto. I feel like vapor/taste is dropping off, so I add liquid to the batting (which looks try after I remove the drip tip) only to over-fill the thing and get gurgling. I've never "gotten the hang" of when/how much to top off without wasting juice. The carto-tank keeps the batting juuuuuuust wet enough, without being too wet and gurgling or leaking out the bottom of the carto. For what it's worth, I can't direct-drip either
It's all about just finding what works for you.
