Would this work?
Just put a tree for shatter for phantasm for lockdown and so forth.
Some of our traits are all over the place. Then rework some GM traits and Minors. and rework some phants too. (iwarden bug, image, etc.)
Ex:
Phantasm Tree would include the empowering illu and phantasmal strength, etc.
Shatter tree would contain shattered conditions and shattered concentration, etc.
I think this would promote more solid builds and not solely putting trait points that are left onto some trees.
While some traits need to be reworked or repositioned (e.g. Mantras, Glamours) I really dislike this idea. It will drastically limit build diversity due to two reason.
First, all Shatter Mesmers go Shatter tree. All Phantasm Mesmers go Phantasm tree. And so on. Yawn. While 30 Illusion is quite mandatory for Shatter builds, they do have some diversity (Offense = Domination, Support = Inspiration). Your suggestion would take that away.
Second, it will also limit the amount of traits you can get to create a build around. You want to go Shatter? Pitty, that all Shatter related traits are in one line so you can only pick three. What would you do with your other points now? It would turn all Mesmer builds in some weird hybrid set up.