Flip sites kinda defeat the 'simple' part of the KISS principal.
I really can't see my irons quickly outside in the dark even with a light, an AimPoint red dot is easy to see
Have you thought about an illuminated front sight post? I just put an XS illuminated post on my AR and its awesome.
I agree with everything that has been posted by Mvician (no surprise there ) Here is my idea of a KISS rifle with only accessories that are necessary to ME and the tasks that I ask of the rifle.
When it comes to ARs, people who usually go around talking about KISS rifles are sending the message that "I have no training, and I don't intend on getting training at any point in the future. I feel I know all there is to know about firearms in general because I own a few and I've even been to the range a couple of times. I'm an NRA member and that makes me an expert in the field. I usually open carry because I enjoy being VERY vocal about my second amendment right in public any time someone looks at me oddly for carrying. KISS rifles? Yeah, I'm sure a Vietnam Era configuration is PERFECTLY acceptable for today's gunfighter."
The only folks I know that hang all the extra junk on their rifles are newbs or mall ninjas.