Hi ! I read your above descriptive requirement of design and developing Windows XMPP, SIP Client in order to integrate Linphone and Spark functionality in to one by modifying existing spark XMPP client.
I have more than 10 years of experience in Software Architecture, C# Programming, Windows Desktop, WinForms, WPF, XAML. I am well versed in VoIP, XMPP.
You can have a look on my profile page. It will be my pleasure to see your message in chat box.
Thank You
Maroof K