This is in fact how Elm does it! Tail call recursion compiles to a while loop.

That does not address the use case where I find tail recursion most tempting. That would be mutually recursive functions.

If the function can be written as an idiomatic loop I probably would do so in the first place.

Right but recursion is only a smaller part of why the optimization is important. It means tail-called functions still build on the stack and long function chains—as is common with fp—can overflow