Set guid on node insertion

Hi,

I'm in the process of doing a bidirectional synchronization using Feeds and Pubsubhubbub between two Drupal installations: let's call one the Hub and the other one the Client.

Here's my current setup:
- hub is subscribed to client's endpoint and client is subscribed to hub's endpoint. No problem with that.
- both Hub and Client have a Feeds Importer to import nodes of a specific type from each other, and both have GUID set as the unique target

Now here is what's happening:
- node is created on hub and sent to Client using a PuSH notification. Inside this PuSH notification, a guid for the node is set to http://hub/node/nid.
- Client receives the new node and adds the guid in its feeds_node_item table
- Now let's say the node just received is updated on the Client: Client will send the node, along with the same guid (http://hub/node/nid) to the Hub using a PuSH notification.
- The Hub will receive the notification and, unfortunately, because the hub does not have a corresponding guid in its feeds_node_item table, will create a new node instead of updating the existing one...

In order to fix this, I thought about adding a feature to Feeds which gives the possibility to set the guid and/or URL of a node in the feeds_node_item table on node insertion. What do you think about it ? Can you think of any other (cleaner) way to do what I'm trying to achieve ?

Thank you for your comments.