There are many automatic memory management systems ranging from the simple clearup of immutable systems (https://justine.lol/sectorlisp2/), to region allocation, to refcounting with cycle collection, and the full-fat tracing.

I'd have thought that allocating a block of memory per-GC type would work. As-per Rust you can use mainly one type of GC with a smaller section for eg. cyclic data allocated in a region, which can be torn down when no longer in use.

If you think about it like a kernel, you can have manual management in the core (eg. hard-realtime stuff), and GC in userland. The core can even time-slice the GC. Forth is particularly amenable as it uses stacks, so you can run with just that for most of the time.