It should already, yeah (unless I'm mistaken...). The various build* functions aren't modeled via protocol requirements so it's a bit more permissive as to what is allowed. @beccadax wrote a nifty result builder which uses #file and #line to dump information about the builder transform.
This has definitely been discussed before. It has a mention in @suyashsrijan's Witness Matching Mini-manifesto, though I'm not sure if there's been any recent developments on that front.