There is also the problem of binary layout. RPC values on binary size, and IPC values on latency with zero ser/des. The two binary layouts are simply incompatib

There is also the problem of binary layout. RPC values on binary size, and IPC values on latency with zero ser/des. The two binary layouts are simply incompatible. You can do zero copy with RPC, but that does not help with ser/des. FIDL uses a full uint64 just for a discriminated union tag, which is just crazy for any protocol that is going through a cable.