Right. I think the two functions should both accept either an iterable of variables or of variable names (the Common Lisp spec would refer to this as an iterable of “variable designators”), and then internally they can translate one way or the other, as preferred. I suppose one could even accept a dictionary of names to variables, since that’s what named_vars holds.
There should be one or more library functions that will regularize these arguments to either an iterable of names or an iterable of variables.