Few things that expect a pointer do it by expecting an opaque dereferenceable thing. Most things that expect pointers actually expect a specific concrete pointer type (even if it's a pointer to an opaque thing.)

IMHO, a language with "real suppport" for handles would use them everywhere, instead of pointers—i.e. make all places where pointers pass through "wide enough" for handles to be passed instead—with reduction to a pointer being a kind of WPO for cases where it's proven to be possible.