It's doable. Had a plugin for it on ST1, but to be honest, it wasn't really much use.
It was cool using xpath/css to create multiple selections though.
The sublime api isn't really thread safe bar set_timeout to queue callbacks in the main thread.
The way I wrote it was a bit crap so it was a bit bumpy.
I'd planned to rewrite it using generators and set_timeout for ui thread yield points, with cancellation on buffer modifications.
But you know, something shiny or something ...
Haven't ported it to ST2 yet.
It is better to remain silent and be thought a fool, than to speak out and remove all doubt