A simple suggestion that popped up in my head while I was playing Vermintide 2:
Ammo Shortage could do one of two things:
Reduce ammo reserves of all player weapons by 50%, OR
Reduce ammo pickup spawns by 50%
This condition would facilitate players to use their guns significantly less as a challenge to make players approach most situations with melee first.
The problem I can think of right away is that lasguns would be significantly favored due to their efficiency blessings and overall massive ammo pool. I think this would be fine, however, as it would encourage players to use different tools to counter the situation, much like how shock gauntlet does encourage the use of maniac-killing weapons.
there was another thread having about 20 modifiers in it, incl. your idea.
the very problem with mission selection is that is all random, if lets say 20 modifiers would be present in a pool, the chance of getting mod you want would be very unlikely.
before modifiers can be added something with mission selection system needs to be changed first, so that players can actively chose modifiers they want and get rewards accordingly.
now low intensity pays more resources and than normal intensity, and i expect less ammo modifier should pay quite a lot as it means less trigger happy gameplay would be required. i am not talking here about just ordo, but pastel, diamantine and emperors gifts as well