AKA: the result of a mind flayer larva being left alone for too long. Amusingly, while pathfinder was legally prevented from including illithids, the neothelid were completely fair game, leading to a bestiary where the latter were just awkwardly shoved in.
25 aberration RHD don't bode too well for playability, sadly. Additionally, anything that'd like being Gargantuan would also like having functioning hands.
The wormbeasts also have a wide variety of PLAs, but those tend to be mid-level at most.
The neothelid's other abilities: swallow whole, improved grab, and a strong acid breath weapon, are not all that impressive when you're a mid-epic character.
Overall, -0 LA. Remove a ton of RHD and this might be more playable.