I would encourage interested folks to go one step further and actually build an AR15. You will gain valuable knowledge and experience and also be better prepared to troubleshoot any issues that might come up by understanding how the rifle actually works. It’s easy and fun if you just take the time. Then you can build it any way you want from the get go instead of buying something off the shelf and swapping out a bunch of parts.
$0.02 from the engineer that can’t help himself from taking things apart.