Web service registration patterns (proxy with multiple client services)

Web service registration patterns (proxy with multiple client services)

I'm in a bit of an architectural bind. I need to build a high speed cross
web service communication architecture that collocates registrations for
the same user type on a single servicing web service, but at the same time
can scale in the future to handle multiple user types.
Here are the main points:
Just a few users of a single user type
Right now just a few user types … but in the future I expect the number of
user types to grow significantly
All users of the same user type must to be registered on the same web
service (they are going to information share within that single service –
ie use that single service as a hub to share data). Due to the nature of
the data they cannot route it through the proxy after the initial
registration.
As users register they will need to initially connect to a single well
known external point (proxy) which will then farm them out to the correct
service for the day. (ie users won't have any pre-knowledge of what single
service will be servicing them that day … they will have to register with
a proxy first and that proxy will direct them to the correct service for
them)
The 2 possible architectures that I'm debating over:
When the user first contacts the "well known external point" it could
simply respond with "your service is XXX … go contact him directly." Then
the user would be responsible for registering with the service that was
supplied.
When the user first contacts the "well known external point" it could
forward the registration information onto the service and that service
could essentially "reverse register" with the client.
In general architecture 2 feels more complicated, but might have some
merit because we're not depending on the user to "do the right thing".
Thoughts on which approach is better? Alternate thoughts?
See the image for a graphical depiction of the two architectures.
I'd post an image but !stack! wont let me reference it because I don't
have a 10+ reputation!
Ha found a way to cheat ... stack uploaded the image ... but wont let me
embed it directly ... here is the link: http://i.stack.imgur.com/c0NC6.jpg