Bootstrap: .custom-switch that adapts to font-size

[01e9]

I would like to have a version of .custom-switch that adapts to text size.
At the moment it's "hardcoded" to rem.

Here is an example https://jsfiddle.net/dfmbe60u/13/
I this example I did full label width switch because I encountered some difficulties while trying to make the switch on the left side of the label, also this is what I need for my current project.

[mdo]

This is coming in v5 :).