There are several different scopes which have a reticle etched in the glass and is viewable even when off/dead battery situation. Don't buy cheapo stuff, but spending about $300 or more for quality optics is money well spent. Optics are superior to iron sights in almost every way.
Target acquisition, target id if magnified, low light situations when the rear peep is too small to see through, no parallax so the impact is where the dot is.
Yes, carry spares, and buy a scope which has an easily accessed battery for a quick change. And in the event of a complete failure or damage to the unit, mount BUIS in coincidence so you can use the pop up irons in a pinch by looking through the dead scope.
You have to consider why almost every military issue rifle and, literally, every competition rifle has optics mounted. I think youre selling yourself short by eschewing optics.