Can I play?
Gotta love the never ending search for "the perfect mod." If anybody were to write a dissertation on the pros and cons of all the mods, the results might challenge the 499 page deeming regs monstrosity. So I'll keep this short as it relates to the information/requirements asked/provided:
Since #4 is "not a deal breaker", I'll just ignore it until for now and perhaps for good unless it comes down to a final choice.
As far as "breaking the bank?" I guess that depends on how much it takes to "break the bank". Over $50, $250, or somewhere in between? My first thought is, depending on what that amount is, is there a need to find just one mod that does the trick. Looks to me like most responses indicate posters have multiple mods, a situation I find myself in as I too have not been able to find that one "perfect mod." So I would suggest, if it fits within your budget, take you two most important "needs" and find the mods that best perform each. Sounds like your first is "compact dual 18650" and second is "reliable TC."
I know you totally want to disregard the Sig and Fuchai 213, but I must say from my own experience, I don't know of any other mod that matches it in size, weight, and battery life. I've run mine 17 hours straight in power mode from 30 to 85 watts and still had battery left at the end of the day. For me, and adding in what I like in aesthetics, it is my closest thing to "the perfect mod." Ah, but the TC! Yep, it has some problems, but.....
I do not do a lot of TC vaping, just one titanium and a SS. And it is a pain switching between the two with the 213. But I have managed to dial in the 213 for my TFV4 mini with the Ti coil quite nicely. Since you only use SS, you might be able to do the same with that. But what I have found for my best solution is that I also have a Lavabox DNA200 that no other TC mod I have or tried can match the quality of the TC vape. As far as the TCR/TFR stuff, I currently don't use/need that, so can't won't comment other then say it seems some have made it work and some say not.
(498 1/2 pages to go!

) Sorry for the length, but it is there now, so.........
IMHO, it comes down to, if you only do SS TC, see how the IPV 6X turns out. If you split between power and TC, consider two mods if it fits in your budget.....and the 213 does fulfill your "compact 2x18650 mod" title. And if you find a mod as compact/aesthetic/long battery life as the 213 that does great/perfect TC, let me know. I'll jump on it in a second regardless of price. Well, almost regardless.