Ok, so I have an Intelivision the original brown and gold system.
I have 4 main issues with the controller and it a remake should be the same size
to fit in the system.
1. The Cord is not log enough and non removable.
There is a port mod that can be done to the system.
2. The disc control does have different functions so
a directional pad that can double as a paddle.
3. Would love to see a way for overlays to be added.( could it power a touch screen say adding a battery in the controller.
4. This controller should be able to fit in the controller storage on the system.
(Bonus) The system itself doesn't have a removable power cord and maybe composite video out.
I currently use a vcr.
( Also) I have extra games and can even loan my system out if you wish 
I though id throw that in there.
Thanks, Chris
Intellivison overview
https://www.youtube.com/watch?v=J5l3lV757bA&t=5s
VCR Method Hook Up
