This is a solved problem: look at how the Lua FFI does it. Lua both is capable of exporting its own garbage collector to its counterparty and has a plug-in system for GC so that Lua can use the counterparty's GC. That allows you to either use Lua's GC for foreign objects or have the counterparty's GC manage Lua's objects.

It's funny the hostility to JIT that some fans of compiled languages have.