I'll say one thing which is going to dictate this thing's LA all by itself: 15 ooze RHD. That alone sentences this thing to -0 with little hope of recovery. Of course, the other parts of this thing aren't helping either.
For starters, there's its ability scores. As is the case with most oozes, it's got nonexistent intelligence, good (but not great) strength/constitution, and abysmal everything else. Its sole damaging attack is a slam that deals a small amount of bludgeoning damage and a small amount of acid (said acid can't be used against non-fleshy creatures, to further worsen it). It can't see stuff more than 60 ft. away, and even its description acknowledges how it's pretty much useless beyond that range.
Constrict and improved grab are probably the best part of this thing. On the off-chance you actually hit something, you could possibly restrain it long enough for your caster friend to throw a Disintegrate at it.
Speaking of caster friends: if those are in the party you're actively weakening it, rather than merely being useless. Spell Siphon causes arcane spellcasters within 60 ft. of you to lose random spells of their highest level. Now, while making that evil archmage lose their Gate or Wish is obviously not without its use, the fact that it cripples your own party makes it unusable. Even in a party without arcane casters, is this really the kind of ability worth sacrificing 3/4ths of your build for?
Finally, arcane oozes are immune to magic, which would be useful if they were dangerous enough to become the target of enemy mages. It comes with two caveats: acid spells heal the ooze (HP is probably the only thing it doesn't lack), and electricity magic makes it move faster as if it were affected by Haste (note that it doesn't gain any extra attacks or such, it just speeds up).
-0 LA is the only possibility here, unless you want to make something that locks your party out of playing arcane casters and is outclassed by any half-decent melee build.