What kind of AR do you have?
The idea of AR's needing to be "clean" to run reliably is largely a myth if you aren't talking about some POS gun. See "Filthy 14" for an example of a properly built AR. You need to lubricate them. Lube is much more important than clean.
https://www.slip2000.com/blog/s-w-a-t-magazine-filthy-14/
I typically shoot my ARs suppressed and still don't see a need to be cleaning them all the time to keep them running. One of my Noveskes I put a few cases of dirty wolf ammo through without issue without ever cleaning it. Keep them lubed and they run.
Honestly you probably will need to replace parts before you need to clean it to keep a properly built gun running. I wouldn't let a gun I was staking my life on go 10K rounds without cleaning it, but you could. Having to keep a decent AR clean to keep it running is a myth.
As noted for a HD gun it is a total non issue anyways. There is no good reason not to reasonably maintain and service a weapon on is relying on for defensive use.
To the OP my suggestion would be to get a BCM. There are other guns that are well made and would be perfectly serviceable, Colt for example. I'd get the BCM for a few reasons. They are quality guns from a company dedicated to providing quality guns and who stands behind their products. BCM offers configurations I prefer to those offered by Colt. Given the market there is no reason not to go with a gun like a Colt or BCM.
For a first AR I'd get a 16" gun. The difference in length versus a pinned 14.5 is negligible and not having the pinned device gives you greater flexibility down the road. I'd get a mid-length gas system. I have come to like lighter guns. For that reasons I'd get a light weight barrel with a KMR rail. A lot of the uppers available now have the KMR alpha and I don't see that as being a deal breaker. Its a slightly heavier and less expensive rail. Something like this upper:
http://www.bravocompanyusa.com/BCM-...ight-Upp-p/bcm-urg-mid-16-bfh-elw-kmr-a15.htm
Put it on an in spec lower, properly assembled with a quality parts kit and you are in business. As noted above, add an aimpoint, a light and a sling and you are pretty well set.