Hello,
I've read your requirements and this is achievable. About the "repeat", you mean that video/audio from Blackmagic cards will be redirected to the virtual devices and from there to Skype right?
I've made some time ago a virtual camera that could feed data from video files(movies , videoclips etc) if you want to give it a try i can send it to you.
Looking forward to chat with you about this.
Best regards,
Ionut