It's an interesting concept to explore, but it would probably be a nightmare to balance. A job having 2 playstyles would solve a lot of the issues people are having though.

DNC too proc-focused? Have a branch that has no procs.
RPR too rigid? Have a more flexible branch.
Want more damage options on AST? Have a branch that increases personal damage while reducing buff usage.

It could be a very good thing if done well and if the playstyles don't have a difference big enough to render one branch worthless.