Very nice work, thanks for the write-up.
Several nice combos being utilized here.
1. High initiative + invisibility + delayed turn, grants 2 turns at once.
2. Phoenix Dive + Elemental Affinity + Pyro skills
3. Rain + Contamination
4. Glass Cannon + Max AP boosting abilities (Adrenaline/Flesh Sacrifice).
4b. This combos exceptionally well with Time Warp too
Of note, 1 and 4 are usable by basically any build and grant all of the AP. Leveraging them and swapping Elemental Affinity to Warlord and including Rage would make a great build for any Physical class too. Such a build would have the advantage of not requiring anywhere near as much Memory, as falling back to basic attacks would be stronger.
I'm interested in trying a build like this now

You mentioned several talents, but you'll really only get 2, Glass Cannon and eventually Elemental Affinity. Since Phoenix Dive comes at level 4, get EA second.
Do you know what level we get a 3rd talent? I think it's higher than level 8. Warlord would be the 3rd.
Trying to guess your build here, sounds like we'd need points in all of the following:
0 Scoundrel: Adrenaline (from Flesh Eater)
1+ Pyrokinetics: Combustion, Searing Daggers, Haste?(max AP increase), other damage skills for Affinity
1 Polymorph: Chameleon Cloak, Shed Skin
1 Geomancy: Poison Dart, Contamination, (Fossil Strike?)
1 Hydrosophist: Rain
1 Warfare: Phoenix Dive
1+ Aerothurge: Teleport (could be from gloves), Netherswap
I'd assume the extra points would either go into Aerothurge, for removing Magic Armor faster with all abilities, or Pyrokinetics for extra % Fire Damage.
Not a lot of free skill points to go around, as we need to gain access to tons of skills for comboing and to use our AP on.
Talents:
1. Glass Cannon (@ level 1)
2. Elemental Affinity (@ level 3)
3. Warlord or What A Rush (@ level ?)
Despite the other talents mentioned, we wouldn't really be able to pick up anything else until much later, and these seem like the most important.
To leverage "What A Rush", you'd have to intentionally lower your health to below 50% before starting the fight to get any benefit, so you'd be counting on finishing the fight before enemies act, or retreating/invis after some kills. Granted, because of Glass Cannon you already are, so this isn't much of an extra burden. Intentionally lowering the health before the fight would be a bit of a pain though.
Stats:
Lots of Wits is a must. Going 2nd with Glass Cannon is a fast death. After that, you might need some more memory for the large number of skills you'd want to leverage.
Any idea what the maximum wits required to always go first is during the current content? I don't think it's a ton.
Unfortunately this spread doesn't leave much for increasing damage, either from Intelligence or Skill passives, but this is probably offset from the large amount of AP.