Removing ammo was the single great decision Firaxis made with nuXcom among other shit. And Gollop wants it back...
Conserving ammo in a mission because you wanted to bring other gear along your ammunition (so you don't have as much) should play a tactical role in the game.
The same backwards, the player should have the liberty to stuff himself with ammo is he wants to level a building's wall with his firearm/laser etc. and create a breach-point.
Not having an ammo limitation and fire that grenade launcher or rocket launcher indefinitely is overpowered in a game that wants range to be important.
Also the existence of ammo scarcity in mission could make the existence of robotic weapon platforms (like S.H.I.V in 2013 XCOM) more valuable and more full of impact gameplay wise with its large ammo reserve and firepower.
Ammo scarcity could mean that the body of your own soldier could be a gold mine if you ran out of ammo, creating situations where tough choices have to be made.
The nonexistence of ammo means there are no ammo types.
And ammo types could prove very important in the game where some monsters would be more vulnerable to a specific ammo type because of their morphology.
The problem with micromanagement for those who loathe it because they played too much dumbed down XCOM could be easily resolved with the ability for the player to make custom gear lists.