I don't feel the ACR needs one. It has overall balance, but it's not like it overwhelms other weapons, much less ARs, in those areas. It has a slightly lower firing rate than some other ARs and has noticeable drop off damage at range.
Even the PP90M1, despite my annoyance at seeing it constangtly, at least has the distinct disadvantages of range, and damage and accuracy at range, making it purely CQC which, sadly, a majority of these maps cater to with either being small in general or tons of clutter, so it's just the dev's fault in crappy mapmaking that it seems OP.
Only the MP7, another I see constantly (along with the UMP45 and P90) feels like it has nothing but advantages, but no disadvantages to itself. And no, comparing it to a weapon that specializes in an area does make it a "downside" for the MP7 itself. At the very least, as brought up by others, it wouldn't hurt to add a little more recoil to it.
