GHC's inliner has a notion of "interesting argument" it uses to encourage inlining of functions called with (I think) dictionary arguments. I think another class of argument is very interesting, by being very boring. Any argument that looks like either
\ _ ... (Con _ ... x ... _ ) ... _ -> coerce x
or
\ _ ... _ -> k
Has a pretty good chance of doing a lot of good when inlined, perhaps plugging a space leak. Would it make sense to try to identify such functions and consider them interesting for inlining?