Just to make you aware, Citrix have re-vamped the licenseing model for MetaFrame XP, so that it works the way you initially thought, Peter!
Instead of needing a server base license, you simply buy connection licenses based on the product you have installed.
Citrix tell me that they're "Giving the software away, free!!". What they mean is that you can now just buy a single software CD, as part of a 20-user connection package, install the software on 20 servers, and the licenses will be pooled across those servers. I'm not sure how useful it is to have 1 user per server, though.
The licenses are:
XPs connection (vanilla MetaFrame)
XPa connection (MetaFrame + Load balancing)
XPe connection (XPa + IM + RM)
Since you must buy a minimum of 20 licenses, there is no actual cash saving, since a connection license for XPs is about $250. It's just musch easier to work out.
The model will remain the same for MetaFrame 1.x, though.
I hope this is of interest.