I was rebuilding coils by week 2...what's taking you so long??!?!

(J/K...)
I'd probably counter the commonly held belief here that mods are the best thing ever. I really dig my VV eGo setups, especially with a mini-pro
tank. I use them all the time...at home, at work, on the go, in the field, everywhere. I only really started using my mod a lot more when I started getting into RDA's. I don't think there's enough of a benefit to the ProTank's to justify a mod...unless you absolutely need the capacity for whatever reason...and even then, you could throw a ProTank on an eGo style just fine, but it'll be a bit top heavy. Performance-wise, I get more satisfaction from a mini-pro on a VV battery than I do a pro-
tank on a mod (or an eGo style for that matter.) That said, I get more satisfaction from a well built RDA on my mod than I do my eGo setups, period. RDA's are a moderately advanced topic, though, and unless you're sure you want to go there and know what you're getting into...I wouldn't recommend it. All this is just my personal opinion, though.
Nonetheless, mods open your options. You can use any non-eGo style carto/carto-tank/atmoizer/RDA/RBA/etc with them without any adapters or awkwardness. They do give you some advanced features like VW, or in some cases, an ohm meter. I'm not trying to discourage you, I just want you to think about why you want it. If it's just for a pro-tank, I'd recommend trying out the pro-tank without the mod first to see if you like it.