A quick way to restore motion after changing iskeyword

I want iskeyword to only affect completion.

I need that in the case of Latex. I want \chi_{23} to be a single object with regard to complition. But changing iskeyword also makes \dosomething{crap} a single object which means I can't get to crap using w.

I know I can reimplement all w,b, and so on as they were in the original form. It is not simple at all. Any quicker way?

Any plugin that already implemented it or something?