I'm not a programmer or Premise expert yet by any means, but...
If you don't want Premise to control the thing with msense, just create a modified webcam like module (there's a few of them in the downloads section).
If you do want to make msense work with it, use the dvd changer driver posted in the download section as a guide; inherit the same classes and copy most of the methods into the webcam like module from above. However, I don't think you can do this unless there is a known protocol that uses html and will talk to SP. For example, is there a method that you can invoke to play a song by browsing to a given web address (where the address would contain the ip address for SP, an action, in this case play, a song id, etc...)? What about a method you can invoke via html that will list all the songs? If you can't use the html method, is there a way to use command line parameters to talk to SP that would do this? What about using telnet? You can use vbscript to invoke actions over html, command line and even telnet (use the virtual Lantronix UDS10 trick to make a telnet connection appear as a virtual serial port).
If you can figure out how to talk to SP, it would be very doable to use Rob Brun's dvd changer module and modify it.
I'm actually wanting to do this for an all complete windows media center module that works with msense. For media center, you can communicate with it using a free program (vmccontroller.codeplex.com/) that can control MC over telnet; the same program can grab artist info, library info etc... All information is received in ascii, so it appears this is very possible for Premise integration via the virtual Lantronix UDS10 trick. I'm not sure how to handle the album covers, but tcpip controller also outputs those over telnet. It looks like someone could write code to automatically generate a library in Premise (i.e. generate a collection of virtual discs). When the user clicks on the disc in AB, Premise would automatically connect to the media center pc source and a script would run that would send the play command for selected media. When I finish my current projects, I'm thinking about attempting this and starting a new thread.