Same here, only building - don't own a stock coil tank. I don't use pre made coils, for my kayfun prime i just wind it myself (28g 6wrap, no effort at all), and for my drippers etc i use pre-made wire, but still wind myself.
I used stock coil tanks before (in fact that's where i, like many others, started) like the Nautilus 2, Nautilus Mini - but just before i was going to pull the trigger on a high end stock coil mtl tank (Kabuki from HoH, $200 and uses Aspire stock coils), i figured i give a Kayfun V3 Mini clone a shot - instantly converted, 6 weeks later ordered a Prime from germany.
I'd bet that most "serious" MTL vapers (as in, not someone who just got off smoking with an MTL tank but sticks with it) use rebuildables.