a non ego tank will not be aesthetically pleasing (IMO) on a 14mm ego battery. You'd most likely not go larger than a 19mm tank, and you'd have to have a decent beauty ring to at least make it look somewhat acceptable.
Little tidbit.. a K1 vapes very close to a nautilus, i kid you not.
There is another option.. the K2 uses the standard (non nautilus) BVC coils also, but it's a 510 connector. it's the upgrade to the K1, however it's only 15mm, so with a readily available 15 or 16mm beauty ring it would look great on the battery. The airflow is different to a K1, so you could try it and see which you prefer.
Now if you really want nautilus coils, the smallest tank to use them is the K3, which is only 18mm, and you could probably get away with it with a nice beauty ring. It's also very cheap, 10 bucks. Just throwing some options out there. If you want more capacity, there's the mini vivi nova which is 16 mm and a 510, but again, uses the standard bvc coils (which are perfectly great).
I'd recommend when budget allows, to upgrade to a battery like a vision spinner or even better, the aspire CF VV+. All aspire bvc coils work fantastic on VV batteries, a wattage control device is not required at all. I'd stick with the 1.6 or 1.8s in any case, but you'll be able to fine tune your vape a lot nicer, for example, i personally find the 1.6 bvc coil is at it absolute best at a regulated 4 volts.
If you are in Australia, i'm happy to give you a K1, but if not, there's no point as it would cost more to ship than buy a brand new one.