Give Engineer and/or Recon a semi-automatic pistol caliber carbine to even out their range. Engineer is very unfun to play as infantry due to the comically short range of his current arsenal (being SMGs and shotguns) so a weapon with better range would be fantastic for his kit. It would also fit the trend of Engineer using exclusively pistol calibers, aside from the shotties. Recon can have it as well because he is sorely in need of more weapons and a carbine would make for an alright CQC gun to diversify his playstyle.

The attached image is merely an example of what I'm envisioning with this.