You could use id/vec indices, instead of directly pointing to your e.g. sucessors: "struct Node { successors: Vec<usize> }". This has the obvious disadvantage that deleting nodes is quite hard though.
It's hard because now you're in charge of building a malloc(3) implementation. Depending how important this data structure is you might need to worry about 1. about fragmentation 2. free space managment 3. adjacency and cache effects
So you've traded on hard problem for another hard problem. Not something I'd call a win.
Trees, indexes (including bitmaps), buffer allocators and even just keeping state in streaming cursors (Volcano model). Are all pain in the ass in to implement.
In fact implementing a Cursor trait for like 10 different Cursor (SrcView, Join, Project, Compute, ...) became painful because each cursor struct has it's own complex lifetime params and those lifetimes were trying to leak into the main Cursor trait.
Right now I can't do that without resolving to runtime using RefCell. In my case the plans could be entirely materialized at compile time, so not really a win.
The situation won't get better until there's some kind of abstraction over lifetimes (HKT?).