Variables application for gap values

When setting variables, it's frustrating when some of my companies themes require 'auto' for the gap value and some require a hard numerical figure. I thought I could use a string value to set those variable values for gap values (it made sense to me since the gap value accepts both alphabetic and numeric values), but I can't. It would be great to update that so a string value can be applied to gap and other spacing values that will accept ‘auto’ as a value (like typography line height).