That ought to do it!
It's going to need a lot of NA since the AC should be better than the Mystaran Kraken, I think. Unless you want to find some other kind of AC bonus (though nothing seems particularly appropriate).
The main argument for pushing the AC up to 40 like the Mystaran version is just the fact that The Kraken actually has an AC 5 points better in the original text! What if we started with your second version #2 (version #3?) and also added an insight bonus? If you like, we could classify the deflection bonus as profane, since it's some kind of exemplar of evil:
AC #4: 40 (– 8 size, +1 Dex, +25 natural, +7 deflection/profane, +5 insight), touch 15, flat-footed 39
(I'm not really certain that it should get the insight bonus when flat-footed since that just seems wrong, but I also don't see in the rules where it wouldn't.)
Did I sell you on that?
It seems like the real problem is that we gave the Mystaran kraken too much AC compared to a normal SRD kraken! I think our best compromise on AC is #6!
Thoughts on the speed? It seems like they're 3x faster than a standard kraken and only a little faster with the jet. It would be something like Swim 60 ft with a jet speed of 320 ft, just using the 2E ratio.
Works for me!Your speed suggestion and the modified fast healing both seem good to me.
Start with the 7 kraken feats, I guess. Do you want to add some epic ones among the next 7?
| Level/HD | Half-Fiend SLAs | Half-Water SLAs |
| 1–2 | Darkness 3/day | Obscuring mist |
| 3–4 | Desecrate | Fog cloud |
| 5–6 | Unholy blight | Water breathing |
| 7–8 | Poison 3/day | Control water |
| 9–10 | Contagion | Ice storm |
| 11–12 | Blasphemy | Cone of cold |
| 13–14 | Unholy aura 3/day, unhallow | Acid fog |
| 15–16 | Horrid wilting | Horrid wilting |
| 17–18 | Summon monster IX (fiends only) | Elemental swarm (water only) |
| 19–20 | Destruction | Plane shift |
SR 30 is good.
I hadn't been thinking about SLAs since the original doesn't have them, but you're right that it seems an Int 19 kraken should have some. And we should deal with those before feats. Maybe it shouldn't be as many SLAs as a regular kraken, though. I'm also not sure about widening some of them --- I didn't think you could use a Widen Spell metamagic feat on an SLA. You can't use Quicken Spell on an SLA; you have to use Quicken SLA. What if we just give it control water, control weather, and either destruction or horrid wilting?

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.