Since you don't seem to be getting the basic concept of why the A2 is the way the A2 is, it's going to be hard to make you understand why the devs have put it in with only long-range optics if you can't even grasp it being supposed to be a side-grade option for the Insurgents that desire its specific function.
Do not pick it if you want something dynamic and versatile, you can pick the AK's for that, or if you want something that has more punch, there's the FAL and the G3 etc, you have other options if you don't think the M16A2 works for your use, so then stop using it.
Insurgents have options that are both cheap and arguably the best guns in the game overall, so the M16A2 isn't supposed to be your "go-to" weapon for close quarters or even close-to-mid range. It has two distinctly popular uses in the game:
- For long-range engagements
- As a "throwaway" weapon you pick just so you get the magazines in your loadout and can just pick up a kitted out M4 from someone that died
This allows you to use the supply points for other things, rather than kitting out the A2 if you think it's not satisfactory (even though it's really freaking good at range when used in a DMR type of role, extremely good for tracking running targets at range), so regardless of opinion on the matter, the M16A2 is working as intended.
Sure, the devs could give it something like carryhandle-mounted rail and then optics on top of that, but they'd then have to design around the increased centerline shifts and account for even more factors like line-of-aim and barrel-line for obstruction.. it would all be unnecessary extra work for the devs just to address something simply because you're not willing to accept that it has a different use than the A5 does and want it to be more modular or affect it's ballistic performance and whatnot..
The ballistics are not to be touched, they are based on physics and working as intended, this is why you for instance shouldn't use the SCAR-H (as it performs ballistically the same as the AKM) if you want ballistic performance but rather use it for the other benefits such as the reload&controls benefits it has over the AKM.
Save yourself the headache and just abandon your desire for changes to something working as intended, and instead complain about things that aren't realistically implemented (i.e; like how many complained the M249's recoil was irrationally bad as the real life gun hardly moves at all, etc).