The Lodestar is the one that I think sounds the most interesting; I actually read the Savant, but didn't like it. Just didn't wow me like I'd hoped it would. The Mahout was interesting as well, but not my cup of tea in general.
Morrus most of those classes are powered. 2 of them at least drastically- lodestar and tinkerer. Mahout was hard to rate the concept was good. Gemini in play was also a lot weaker than a basic fighter/thief in actual play. The PC was retired.
Have you done a survey if people are using these classes?
The savant and the fatebender are both classes I’ve already considered playing (but haven’t found the right game for them yet). The gemini seems interesting, and I’d consider it. The lodestar seems interesting but requires way more bookkeeping/tactical mapping than I’m up for. The others range from “meh, not my style” like the mahout and gunslinger to “I don’t think this should exist in D&D” like the tinkerer and the bloodweaver.
Okay, first off, the answer is probably Tinkerer, second choice Gemini. It would be 1000% Tinkerer all the way, if it had a cooler name like "Artificier" or "Engineer". Now my thought process:
Hmm...to me Bloodweaver occupies the same conceptual territory as Warlock and Fateweaver occupies the same conceptual territory as Wild Magic Sorcerer, so I wouldn't play either of those as I'd just play a Warlock or Wild Magic Sorcerer instead. (I mean to be clear, looking solely at the content in core, I would never play a Green Knight Paladin either because it is conceptually way too close to Ranger or Druid/Fighter; if concepts overlap, I will always go for the way of executing that concept that's older.) Same with Geomancer and Druid although Geomancer reminds me of the class of the same name in Final Fantasy Tactics and scores some style points there. I'd have to compare the Gunfighter with the (I think) official Gunslinger class that (I think) WotC released, but then again I'm not conceptually a fan of either one cause I am fine with firearms in my D&D fantasy, but I don't like them being as-good-as or better than medieval weaponry.
That leaves Tinkerer which is an artificier a character type I know I've always wanted to play. Gemini, Lodestar, Mahout, and Savant are the class ideas that don't overlap, in my mind, with any of the same conceptual territory as the core classes. Of those, Gemini, Lodestar, and Mahout all seem like cool ideas but Savant I'm not too much of a fan of. It's basically "Sherlock Holmes as Played By Robert Downey Junior" the class, it seems like, which is an archetype I like, just not one I'm sure is well suited for the D&D fantasy setting. Also the Savant description reads too much like "super great at everything" for my tastes: if it's balanced so it actually is as good as it sounds, then it's broken and everyone at the table will hate me if I play one, and if it's not, it seems there's a high chance it will be spread too thin to be much good at anything, like the pre-5E bard.
Given these options, I would have to read them more closely in order to say for certain. I consider any class to be a liability if it is utterly incapable of healing anyone, which looks like it would disqualify all of these aside from the Bloodweaver. On the other hand, blood is icky, and I wouldn't be comfortable roleplaying that concept for any great length of time. The geomancer looks like it might have some healing in there, somewhere; or else possibly the Mahout, if they can get a unicorn or something.