You're proposing to plug the mouse and keyboard into the TV .... instead of the stick? It sounds like you want to have the TV act as a KVM switch, which seems a bit odd unless you plan on having multiple sticks installed... I'm guessing you're in the very far minority that would want that.
Aside from that, TVs really do need a new connector. HDMI already supports full HD, 7.1 audio, ethernet, and CEC. There's enough there to let the stick control the TV, and get network service from the TV.
The power want is pretty reasonable in the general case, and I've wondered about it in the past... but do take a closer look at this stick in particular. It wants power from a 5V micro-usb. If your TV has a USB port for firmware updates, it can probably already power the thing. For TV's manufactured in the last 5 years, the odds are pretty likely.
Cheers!