Hi
In my limited understanding you can have SQL Anywhere running on a server and all your users connect to that. The server license would need to be licensed to the number of users. You would need to talk to SAP about the licensing implications.
However, if you application is designed to use a local DB it may not be applicable to use a central server license. So you would need to have a local DB file fo each user on the citrix server. So the database files would need to be in the user environment. Your application would need to connect to that database. I do not know if that would really work in a terminal server / citrix environment or what the licensing implications would be.
Firstly I would try it and prove it works before committing to the strategy, I would create a virtual windows server and a few users and prove the each user could RDP in and run up an application connecting to a separate DB at the same time. I would look at the memory usage per user in order to understand how that might scale up.
Finally, why not more the SQL Anywhere DB tables into the Oracle DB?
Hope that helps.
David