Personally I'd like to have 2-3 vision modes (night vision, thermal, UV, etc.). Could make for some interesting enemy engagements and/or environmental situations too. Also, a few different flashlight/headlight/fog light/etc. configs for the frames so peeps could choose the one they like the best for them. It also adds customization options which peeps usually like to play around with.
Now with that said, the light configs probably wouldn't be too difficult of a thing to add to Em.8ER, or too expensive. I'm unsure about different vision modes though.