I agreed with the randomized loadout for better rewards, but I do not agree that there are only 3 weapons for each primary, secondary and melee section because there are chance the weapons are actually outdated, useless (Stug I am looking at you). And I can imagine how hard and how much time needed to be taken to revisit all the older weapons to be usable or buffed/balanced properly.
The suggestion I can think of in mind, keeping the randomized loadout but utilizing it at the maximum, is reusing the sortie's Weapon Type/Category section this should retains the archimedian difficulty, keep the loadout specified to a certain category which requires player to diversify their loadout but lesser issues due to the outdated weapons.
e.g
Primary contains bow, beam weapons, launchers, assault rifles, crossbow, shotguns etc.
Secondary contains Throwable Knives, dual pistols, single handed semi auto/full auto, beam weapons, shotguns, launchers etc.
Melee contains rapiers, hammers, swords, dual swords, daggers, knuckles, throwable melees, scythes etc.
They rotate every week, for 1 category:
e.g Week 2
Primary - Assault Rifles only
Secondary - Throwable Knives only
Melee - Swords only
In short, it's the sortie modification.