Thanks for the analysis. Being a half feat that boosts my casting stat is definitely a strong point in the feat's favor, it just seems like every time I look at this feat I alternate between thinking its neat and wanting to build around it, to worrying that it's negligible and I'd be better off with a different feat or a straight +2. I think last time I asked this question, the general consensus was that you really needed to be in melee leveraging that last bullet point to make it worth it.

Considering that I'll need to pack other spells for fire-immune enemies, I probably don't need Elemental Adept. Usually people seem to recommend getting either Elemental Adept or Flames of Phlegethos, but not both. If I encounter fire-resistant enemies, I can just fall back on my non-fire spells.

I'm also wondering if such a build can actually tank; yeah, they might be tough, and they might punish attackers, but how do I actually get people to attack me in the first place? Or maybe I'm better off not being attacked. But if I want to tank, it feels like I'd need to pick up both Warcaster and Sentinel, so that I can punish enemies for moving away or attacking someone else. I kind of need Warcaster anyway, so I can cast with my hands full. I think GFB is eligible for Warcaster's OA replacement, so long as I don't have the flame jump to a second creature, but I might pick up BB as well, just in case (also doubles as an option for fire-immune enemies, if I'm stuck in melee).

I'm also not sure if it makes sense to get both Fey Touched and Shadow Touched. I know sorcs are always wishing for more spells known, so that's why I mentioned them, but if I just need a half feat, then there's also Telekinetic and Telepathic. However, this might mean not getting something else, like Metamagic Adept. Instead of two half feats, I could take a +2 and something like Metamagic Adept. Hmm, is it better to get four more spells known (each with one free casting per long rest), or one more metamagic?