The Loot Box mod would be top-tier.

Could some of the weapons from the Rim Effect mods be added, such as the alliance weapons being uncommon and the Lancer and N7 weapons being legendary?

I would appreciate materials from the Expanded Materials - Metals (by Argon).

Personally, I'd separate the metals into the following categories when choosing what to put into Rewards.

Common Materials: Iron, Coal, Copper, Tin, Bronze, and Lead
Rare Materials: Tungsten, Titanium, Chromium, Stainless Steel, Germanium, and Lithium
Fossils: Fossils and Dark Oil

Ideally, I'd like a wave reward that gives me a modest amount (based on reward rarity) of each material in the categories. Now, this is a mod that could really bloat the reward screen if you gave it a full VWE treatment the way they do for things like Steel and Plasteel in every single category, so if you're not looking to make a dozen new reward for every tier, I'd suggest instead having 1 Normal reward that gives a quantity of each Common Material in slight excess of the equivalent tier Steel drop (as these materials are not as useful as pure Steel). And then 1 Excellent reward that drops a quantity of Rare Materials of roughly the equivalent amount of Plasteel for the tier. Fossils probably belong as a Good reward of equivalent quantity to the Steel drop for that tier.

There may be a case for adding quantities at their reflective reward values, (e.g. a small amount of Rare Materials at Normal, and a large amount of Common Materials at Excellent) but I'll leave that up to you.

@Natalie6 The already existing Random Weapon rewards can potentially carry Rimeffect weapons in them since they dynamically pull from all weapons in your game, in case you weren't aware. But having a dedicated reward for specific high-level Rim Effect weapons could be neat.

I'd also like to submit SRTS for consideration.
Getting a single copy of one of the smaller craft would make for solid candidates for the Good reward slot or better.
Maybe one of the upper-tier craft like the Pelican as a Legendary reward.

Android Tiers SM8 Legendary Reward, or a T5.

Insectoid Genetic Lab from https://gtm.steamproxy.vip/sharedfiles/filedetails/?id=2706534548 as as normal/good reward

posting for myself so I don't forget, rewards can trigger events. trigger shuttle crash as poor as alternative to resources

I have no idea if some of them exist but anyway

Mortar Drop (Normal)

— One Mortar and 10 random shells

Mortar Drop (Good)

— Three Mortars and 40 random shells

Mortar Drop (Excellent)

— Five Mortars and 25 of each mortal shell
(25 of HE, 25 of Incidenary, 25 of EMP, etc.)

(If using Combat Extended mod; use 81mm mortar shell)

Reinforcements (Normal)

— Allies will drop in to help you with the next wave.

Power Drop (Poor) Requires Vanilla Furniture Expanded - Power Module

— Two Small Vanometric Power Cells.

Power Drop (Good)

— Two Vanometric Power Cells.

Power Drop (Excellent) Requires Vanilla Furniture Expanded - Power Module

— Two Large Vanometric Power Cells.

Persona Monosword Drop (Legendary) Requires Royalty DLC

— 1 Persona Monosword (Legendary quality)

Double Reward (Normal, Good and Excellent)

— Two random rewards of a worse grade (Instead of having 1 Good reward, you get 2 normal ones) Cannot pick another Double Reward.

Triple Reward (Legendary)

— Three random rewards of Excellent quality. Cannot pick Double Reward.

Hero Pawn (Legendary)

— Get 1 young Pawn decked out with all Archotech bionics, some other bionic implants, >10 level skills and lots of passions.

Achievement Points (any grade) Requires Vanilla Achievements Expanded
— Unlock an achievement that grants you 20/50/75/100/150 achievements points. (Maybe put like… 5 copies of each achievement in case we get that reward again.)

Also weapon drops are a bit useless if you’re using Combat Extended, as these weapons drop with no ammo.

Relationship Boost (Good)
— A random non-allied faction becomes your ally, if you can ally with them.

Relationship Boost (Excellent)
— Three random non-allied factions becomes your ally if you can ally with them. Guaranteed reinforcements for the next wave.

Spacer Armor Drop (Good, Excellent and Legendary)

— Get 2/3/4 random powered armors (Marine, Recon, Locust etc.) and 2/3/4 random powered helmets. Their quality depends on the reward quality (Legendary reward drops Legendary quality armor.)

Also if you're using Combat Extended then Weapon Drops should include ammo for the dropped weapons.

...I'm not sure if that would be 'More Rewards' but I'm still suggesting it :v

a 1.6 update winston is my favorite storyteller but these would be a welcome change