I don't see how what you describe doesn't in general apply to FFI between any languages with different resource management philosophies. In particular:

> Yes, in Rust you can implement the Drop trait, but then the caller needs to remember to put the object in its own block...

Why would you need to remember to put the object in its own block? If you want to manually control deallocation, just call drop manually (or put the object in its own block if you really prefer). If you don't care, just let the Rust compiler pick a time to drop. In both cases, the most important guarantee – that drop doesn't happen while references to the object live – is still upheld.