Now, I do teach middle school, and some pretty unique ones at that... but I find that *if* my students have an idea on how to tweak a gesture, they'll usually speak up without my even asking.
For example, today I simply made a "c" with my hand to stand for the "conclusion" (because we use Step-Up and you write a "C" on your outline anyways for it) and I had a student immediately say, "Wouldn't we do this...." and she rolled her hands (like "wheels on the bus") "...because you said the conclusion 'wraps it up'?" Typically, I go with it if a student gets excited about a change or a tweak, unless it just makes no sense. I loved it!
I'll be honest with them if I am having trouble coming up with a gesture, and they are often good at giving me a fresh perspective-- -but I'll be honest...I don't even usually have to ask...because if they have an opinion or idea, I'm gonna hear it!