[kstenerud]

My answer would be to create a shortcut in the existing reference system of the gc. Invoke a subset of the gc which checks a reduced list of object references made from that scope or deeper.

Reference counted systems only work if you don't create cyclic (strong) references, so that argument is moot. In fact, reference counted systems can deal with resource objects easily so long as the compiler/interpreter ensures that pending autoreleases are executed when unwinding the stack during an exception.