I use a Kayfun clone on my variable wattage device and have no desire to change to anything else. There's no need to use a mech for the type of usage it sounds like you're looking for.
I'm going to agree with the person earlier in the thread who recommended an EHPro Kayfun Lite + clone. It will run you about $40, and with about $10 in supplies (wire from amazon and sterile cotton balls from CVS), and a couple bucks more in tools (pliers or tweezers, a butane lighter, a drill bit to wrap your coils on), you'll be set up with everything you need to use it for a year or more. No more buying consumables like coils or cartos.
It will take a few coil builds at first to figure it out, but once you've got that down, a coil you build in 5 minutes will last you 3 weeks or so and you'll spend another couple of minutes every few days changing your cotton. And the flavor is MUCH better than your protanks.
The reason the guys at the store said you'd want a mech mod is that a mech mod with a dripping RBA is pretty much the standard build for cloud chasers and a lot of people equate rebuildables with clouds. I use my RBA tank (the Kayfun) and my dripping RBA (an Igo-W) on my eVic and they're great.