I think the only way to link the market wards would be to link them by search counter only.

I have a strong suspicion that the problem lies with wards being zones. If you made 1 giant ward zone you would still have the problem of not being able to place a bazaar due to over population of retainers.

ANother problem would be being in Grid, searching for a item which happens to be in Uldah, enter the correct ward and exit in Uldah. It would be abused for quick, free transportation.

So I think the only way to link wards would be to link them by search counter only. If that is a problem with the current client I have no idea. But probably is since they haven't implemented it from the get go.

I agree a global chat channel and linked search counters would go a long way to alleviating Uldahs congestion.