Well what I really want is a best of both worlds situation, because I don't see the problem with having duty sets which allow you to access endgame on BLU. Also why use sharpened knife when Khlastral exists and has longer range, especially on things that cant be stunnded thats better unless you need the weave. Ultimatelty I believe all of it to be an illusion of choice, theres already a clear best way to set up your 24 spells if you're after raw damage, and tank blu does so little damage theres a clear best for their set up too which is just assisting others, and I'll aggree its a neat concept, but not one thats worth the limited status IMO, I don't find clearing dungeons with BLU set ups to be particularly more fun than doing it on other classes, theres a reason some CC's have been phased out of the game, and its because they are not optimal or fun to use a lot of the time and when the novelty wears off, you'll just run whats most effective, not like theres much real variation anyway.
But tangent asside, what I would want is for blu to be a normal job with learning spells being like bard perform, something thats updated along the side, as you said you're just picking what shape aoe it is, so the system could just be "make sure you pick an astral an umbral and a physical" before it lets you in duties, the current illusion of choice doesn't do anything for me, as I don't find death skills fun, sleep has been not good CC since ARR, and the other CC other classes already have and are not excluded.
You've not taught me anything I didn't already know, I just don't see value in what you are claiming has it, I dont care about the shape of my abilities particularly so theres only 3 choices for the filler, the rest is just common sense for damage and optimising