How to send outbound messages only through some Edge servers and not others

I have an Exchange 2010 infrastructure with multiple Hub servers and multiple Edge servers; all Edge servers are subscribed to the organization and are used to deliver both inbound and outbound messages.

I need to perform some pretty invasive maintenance on the Edge servers (full O.S. patching, Exchange SP2, FPE rollup, etc.), so I'd like to remove each of them from the mail flow, get it in shape and then put it back. But I also want it to deliver all messages which have been submitted to it, without losing any of them.

Removing the server from the inbound mail flow is as trivial as deleting its MX record from the public DNS; what I'm looking for is a way to remove it from the outbound mail flow: I want the hub servers to send outbound messages only to the other servers, not to the one I'm currently working on.

The following solutions don't work:

• Removing the Edge subscription: the server is rendered unable to send anything to the Hub servers, including NDRs; also, this causes Shadow Redundancy to kick in and re-send all messages queued on the removed server, causing message duplication; definitely not what I want.
• Removing the server as a source server for the outbound Send Connector: this causes the still-queued messages on the Edge server to not be delivered, because the server loses its outbound route for them.
• Disable the Receive Connector on the Edge server: this also causes Shadow Redundancy to kick in, because the Hub servers can't poll the Edge server for delivery acknowledgements.

I know there is a hidden Send Connector which tells Exchange how to route outbound messages to Edge servers; this is what I would need to configure. But I can't find a way to get my hands on it.

How can I bypass a specific Edge server and only have Exchange send outbound messages through the other one(s)?