I personally do not feel that there is too much content that they should add. While a melee system is always fun for rubbing it in people's faces, I personally would not want to see it implemented. It's easy enough to brag with pistol kills. I also would not want to see an air strike. The idea is very CoD heavy and when the game is built off of "infantry combat" an air strike would slightly defeat that purpose. What I think INS needs most is all mechanical. I want to see hit boxes fixed so that you can actually snipe somebody's head when they're prone. I want to see character models the same size as the width of your screen so you don't get stuck on random stuff like doors, boxes, or even that flat surface in the middle of the road. And I want the draw distance turned into a sphere so that turning away from your target doesn't let you see them more clearly. This also eliminates the extra advantage that high ground gives you based on the draw distance.
This last one isn't horrible but I still feel should at least be mentioned, I'd like to see the teams evened more. For instance, because the majority of the insurgent team has access to fully automatic weapons, it gives them an advantage at indoor combat. Spray and pray works really well when you're only looking for one bullet. I think should be offset by accuracy. Currently, every gun shoots perfectly straight (except for the shotty) which means as long as your sight is lined up properly you can't miss no matter how far away you are. I have heard people say the marine weapons are more accurate, but in practice I do not believe this. I've sniped with the AK-74 as well as snipers have. If weapons had slight spread on them it would make camping far off in the corner much harder to do, unless you're a marksman.