I use F12 throughout the day to open iTerm and Cmd+F2 to open Spotlight, and the escape key is obviously generally useful. Losing equivalent dedicated buttons/shortcuts would be a dealbreaker, but otherwise I could take or leave the function keys.
Edit: If yes to the above, are there any situations in which my configured dedicated buttons might conditionally disappear?
System Preferences allows you to do some limited customization of what buttons show up, including adding a dedicated Spotlight button. (I replaced the Siri button with that on mine.) See: https://www.howtogeek.com/303733/how-to-add-or-remove-icons-...
Beyond that, BetterTouchTool allows more advanced customization of the touchbar. I've never used it, but it's worth a look. See: https://www.howtogeek.com/307468/how-to-add-custom-buttons-t... and https://folivora.ai/