Unturned 3.0 had quite good weapon diversity, although it was missing one major type of weapon up until the release of France. Battle Rifles.
Seeing how 4.0 will have reworked ballistics and more realistic ranges, battle rifles seem like an even more viable and meaningful addition. A middle ground type of weapon, between assault rifles and DMRs, battle rifles could be ideal for survival PvE and PvP scenarios.
Having a full power rifle cartridge of a DMR compared to an intermediate cartridge of an assault rifle, but with fire rate, accuracy and magazine size closer to the assault rifle, it would be good at ammo conservation in long range engagements, yet it would still be fairly useful in CQB.