Thank you for reaching out to us on our online Answers forum. I can understand why you are contacting us with these questions and I would be glad to answer them.
For you first question the main reason we did not include HDMI inputs is due to HDCP. We currently have a new Slingbox 500 out which has HDMI connections.
To answer you second questions it probably wouldn't work to well since you can only assign one remote at a time to the component input. If you were using multiple sources you would have to change the to switch remote, then switch to the remote that controls the cable box or DVD player. It certainly can be done just it would be very time consuming.
Here are some links to look over:
I hope these help out.
The Sling Media Moderation Team