The problem is two-fold: First, I'm pretty sure that isn't going to happen. You're going to keep fenangling the arcane tree until reacting to AM procs is an essential part of the gameplay. Now this was fun back when the metagem produced an occasional overpowered burst that players typically used on arcane missiles. But read that again, it was fun because it was overpowered. It was not fun because I was compelled to stop what I had already decided was the best course of action, to cast the spell that a RNG told me was a good idea. You're not just going to reinforce this horrifying Simon Says design, you're serving it up to the newbies at level 2.
The second problem is even worse: Arcane has Barrage, (bringing the number of instant attacks up to 3, ice lance is still super strong) which doesn't do anything of consequence in pvp, and arcane blast, a spell that is only relevant when the mage is unharassed. Sure, this is a delightful design for the arcane tree. PvP with arcane is like a horror movie version of Where's Waldo, and I'm the sorority girl who just acquired biblical knowledge of the opposite gender. The problem is that that one spell isn't quite enough to make the tree meaningful. Arcane needs something else, not to give it more power, but just to give it a little more identity. With the Arcane Missiles spell permanently locked into some kind of mindless 'smoke em if you got em' design, there is nothing to arcane beyond casting arcane blast and praying to the Gnome Surgeon God.
I was among those who petitioned most strongly for arcane missiles to be improved. It was too costly, and telegraphed the mage too well. The problem is that the new design is a regression. What little was useful about arcane missiles was discarded, (extra range, tracking, can't run through the mage, psychological pressure) and nothing whatsoever was given in return. In fact, it's massively weaker and requires even more talents than before to become useful. If it's now supposed to be a mana tool, then locking it at a 40% proc is logically indistinct from simply giving us more mana. Either way, choice does not exist.
I'm not averse to this spell being a mana tool. But, there are easier ways to do this, without ruining the spell itself. It could just be a lot cheaper. Clearcast could be changed to half spell cost on the next two spells, so the mage could choose whether to cancel the current spell and cast two cheap arcane missiles, or continue the current spell and get one cheap arcane missiles. Arcane missiles could have a much longer channeling time by default, like 8 individual bolts, but cost a lot of mana, so clearcasts are very rewarding. AM could maintain the AB debuff, and each wave of AM could proc clearcast or some mana regeneration effect. Barrage could have it's damage powered up, with AM casts being the only means of reducing it's cooldown. (Frontloaded option with Pom instead of AB backload)
Many things are possible, but the current implementation is giga pudding bad.