Jubaku: San is the only spell they should have released, and even then, it's not imperative. Just because you take an extra two seconds to land a spell doesn't make it any less useful. Learn to time it better, after all, you had to learn to time migawari.
Utsusemi: San was given out with kyahan +2, just not directly. Even so, even if we did have San for 6 shadows at a time, magic would just wipe it, and VW mobs that matter typically take 2-3 shadows a swing anyway.
If we're talking for utility let's first sound lucid and coherent, so people can at least understand the jist of our points.
What does ninja lack harder than any other job for content that matters? MDB. If adding spells, add a magic shield, something that either bypasses the 50% MDT cap, or something that adds direct MDB as most of the gear available for NIN is either DT or MDT, and without using Oupire's katana fulltime, or questing one MDB katana offhand, NIN caps at twilight torque / merman's earring x2 / Merman's rings x2 (alternatively higher MDT dark rings, but, good luck getting one you'd keep), Lamia Mantle +1, & Denali Gloves. Even with that gear, a good TP move > spell, or vice versa, and you have a dead ninja.
They added Kakka: Ichi to fix the TP loss/hit for DW. We already swing fast enough, and there just isn't a point to adding more other than "I want 100-katana".
Phalanx, stoneskin, aquaveil are all alternative spells for NIN that would help them tank higher level VW stuff, especially if stoneskin was on the same recast as say Ichi.
A ninjutsu that follows the rules of baramnesia but actually works to negate the effect also works for monsters like Kaggen who would kill you instantly after amnesiaing / silencing you.
A ninjutsu that follows the rules of barsilena, but actually works.
A healing ninjutsu even.
See? All are viable options that, depending on recast, would not break or change the game as it is, other than giving NIN a standing chance to be asked to tank some of the current end game content.