I need to enable NAT Redirect/Loopback on my Arris TG3482G.

Actually, most retail equipment does have it enabled, and having the feature disabled is the exception to the rule.

So again, how do we get this standard feature enabled on the device.

Not in my experience.

Again. You can't. Sorry that I can't tell you what it is that you want to hear... Get your own equipment. Good luck !

Good luck.  .  They know everything and no one else does so you're stuck.  They won't even let us control our own wi-fi channels because their brain is obviously smarter than ours, even though it will pick the same exact channels on both 5 and 2.4 as your neighbor who's router is 15 feet away one floor above...but hey "comcast smart".

Loopback isn't need for most people but it should be available and easy for people to turn on.  There is no massive security risk, it's  "male cow".