If you use any of the more direct API sandbox/studio UIs, there are already various sliders, temperature (essentially randomness vs. predictability) being the most common.

The consumer-facing chatbot interfaces just hide all that because they're aiming for a non-technical audience.

I use a cheap MIDI controller in this manner - there is even native browser support. Great to get immediate feedback on parameter tweaks

Maybe a Turbo Think button that toggles between Ultrathink and Megathink.

There are already many such adjustable parameters such as temperature and top_k