The stock knob is screwed on, and the factory uses loctite, so some real force may be needed to loosen it. There are dire warnings that excessive torque twisting the shift lever will result in transmission damage, so the directions include holding the shift lever securely with a padded wrench while unscrewing the knob by the base with another padded wrench.
If it just unscrews by hand, than I guess none of the above matters.
Not having a stock knob to study, it would help me to know if the threaded insert in the knob is right at the base of the knob, or is it well inside, and the knob extends over the larger unthreaded portion of the shift lever.
I noticed some pics from my website that were posted at:
DIY wooden Shift knob.
These were made mostly for BMW and Mini shifters, but could be made to fit others if I knew the specs.
There might be some interest in Corian knobs; heavy like metal, but not a problem with heat or cold.