for example  (JUST EXAMPLES)

someone can think

most useful and universal weapons in different conditions will be

for Company size units/operations  
  company support weapons can be
   - HMG while can fire on air target
   - 60mm light mortars because are lighter than 81mm
   - Sniper section with five sniper team with Standard calibre sniper  rifles which can be send to Platoons /Squads because are more universal than heavy sniper rifles
for Platoon as part of this company
   Platton can get Mortars , HMG or Sniper team from company
   Platton can have his own support weapons
     - RPG squad with for example 3 teams which can be detached to squads (because RPG have ability fire different Grenades)
     Squad in platton have one GPMG as a more universal support weapon and 5-7 soldiers with assault rifles with grenade launchers (rather than current 2x SAW , this squad will have more maneuver soldiers)


or someone can think

in Squad just weapons with one calibre for example Soldiers have Assault rifles with grenade launchers , and carry LAW/RPO (because rifles are more universal and better in urban operations , and LAW/RPO dont need special operator)
in Platton , Platoon support weapons will be pair of HMG for his range and fire power , and pair of Snipers
and in company , ATGM  as AT reserve and 81mm mortars better for his range

or someone think

Squad with support element (SAW for better fire power with standard rifle bullets ,Sniper for long range fire ,LAW/RPO for AT and support fire ) and maneuver element (soldiers with assault rifles)
In Platton , Platton support element GPMG  for better fire power on this level ( , Heavy sniper rifle because for range and 60mm mortar (for firing , mines, flares, smoke)
in Company for example AGL (becasue have more deadly fire power)

this JUST EXAMPLES

which weapons are mus useful ? and most universal in different types of operations ?