Can I use my own characters in a Scenario?

I believe the answer to this is "No", but my company has come across a unique request from a client. We'd like to do a Rise scenario, but the client says it will not pass their legal department because they do not "own" the rights to the Rise stock characters. 

So my questions are:

1) Is there any sort of workaround for using my own characters (that my client would own) in a Rise scenario? It looks like the only option is to choose the built-in characters.

2) If it's not possible to use my own characters, is there some way I can get permission (in writing) from Articulate that would give my client permission to use the characters?