Allow cyclic references

I have a content type named A that contains a cck nodereference field that provides a reference to itself and other "grandparent" content type named B which doesn't have any reference so the hierarchy can't go further, this is the top level. The hierarchy is something like this:

- node 1 of type B (Grandparent)
- node 2 of type A (Parent) references node 1 of type B (Grandparent)
- node 3 of type A (Child) references node 2 type A (Parent)
- node 4 of type A (Grandchild) references node 3 type A (Child)

I've noticed that the current code doesn't allow to have cyclic hierarchies, so I commented these lines of code on line 327

if (in_array($parent_referenced_type, $type_names_in_lineage)) {
continue; // avoid cycles
}

and line 334

//if (!in_array($referenced_type, $type_names_in_lineage)) { // avoid cycles

now I can set the reference path to itself several times. Now, this is partially working, except for two things:

- The first select box (Grandparent) should display only nodes of type B but there doesn't seem to be any way right now to filter the displayed values on the first row
- Second, when selecting the Parent, the Grandparent reference disappears and the Parent Reference becomes the Grandparent, this isn't like the behavior I expected.

I would like to contribute but I need some guidance or someone who points me somewhere to start in order to solve these couple of issues

Thanks