Given that True Resurrection, which does not need the body, is not on the whitelist of functional revival methods, it seems the in-universe obstacle is that the soul is in the succeeding Phoera/Vazaalka, and thus you engage in the same "magical fuzzy-logic guarantees your replacement indistinguishable" system as a Globe of Annihilation, and unlike most such mechanics the problem is that the soul has a different life. Which implies the possibility of manufacturing new candidate souls from Miracle creating a replacement that has the Jade Phoenix Mage levels, and any such Phoera would appear to be a valid candidate. You could have a high-level party with at least one other Jade Phoenix Mage easily justify a Phoera "line" that keeps recalling who they were via Rite of Awakening, thus remaining the same PC because of RAW-compatible reincarnation stacking in horrible abuse of what's supposed to be campaign-guiding fluff text rather than a serious character mechanic, in a cost-saving that's not the worst way to spend three levels.

Stats-wise, we have -14 Str, +8 Dex, -6 Con, -2 Int, -4 Wis, and +4 Cha relative to a Treant for the Phoelarch, for a net -14, having an at-will Standard Action two 4d6 Fire damage Ranged Touch Attacks with 50 ft. range plus a 1/day 10-minute Produce Flame for 1d6+5 attacks, up to 10 of which COULD be 120 ft. range if a solid 10 rounds of back-to-back use, and basically free Flaming Weapon on melee damage... Versus a Twinned 6th-level spell at will which makes more of their base statblock, nominally CR 8 creatures. To say nothing of the advantages of being Huge in the Big Dumb Beater niche, which the Phoelark is near-certainly stuck in because 7 RHD. If we're comparing other monsters, I can easily see this being debated as a choice at 5 RHD and DLA -2 against the stand-outs down at ECL 5.

For the Phoera, however, I'm mystified at it being classed -0 the first time, because "oh, you can't source Fire damage yourself" means nothing when you can just sit on a torch. Fire is extremely easy to get ahold of. Always-on +1d6 damage from any damage source available to it, with a not-trash Natural Attack routine to start off with, a good spread of ability bonuses that work well for anything it can do with the absence of hands, Natural flight's still a decent advantage this low...

Oh, and the Cold "equivalent" can easily turn obnoxious because that's a Con-based Fortitude save vs. Shaken on Bite and Claw attacks. One may at first think that's just three shots a basic -2 to some stuff, but no, it may in fact be seven, because Girallon Arms bound to Totem does not sanity-check against "didn't you already have Claws?" by RAW and is a physically different body part from the ones giving Claws here, and you can stack Fear with it, which forces rounds wasted running away on just two failed saves.

So I'll suggest LA +0 on the Phoera because it's at least fine for a range of classes, and LA +1 on the Vazalka just to curb the trivial Fear stacking issue.