You could use Fil-C in combination with a memory-safe language like Rust to allow for both "safe" leaf references (potentially using ownership and reference counting to represent more complex allocated objects, but would not themselves "own" pointers to Fil-C-managed data, thus avoiding the need to trace inside these objects and auto-free them) and general Fil-C managed pointers with possible cycles (perhaps restricted to some arena/custom address space, to make tracing and collecting more efficient) to be contained in a singke origram. Due to memory safety, the use of "leaf" references could be ensured not to alter the invariants that Fil-C relies on; but managed pointers would nonetheless be available whenever tracing GC could not be avoided.

This would ultimately save much of the overhead associated with tracing GC itself.