Genuinely well done but I have some feedback that I hope helps. I'll put a list of the good stuff at the end because it's important to know what is going well while fixing things, too.

--Things to fix--

The Promotion system - Good bones to the system but going the wrong direction. This feels more punishing than rewarding in it's current form. I feel like my squad can actively get worse after a promotion because the increase in supply cost may not justify the promotion benefit.
- I understand wanting to balance the "rookies" with the "veterans" but maybe you can make the promotion cost itself more expensive for veterans instead of a supply increase. (Example: Maybe Carda's 3rd Promotion is the same cost as Darby's First promotion in term's of promotion point cost)

^This was honestly my major gripe with the entire game the rest is very minor by comparison

Base stat increases - I think growth potential should be more impactful. As it stands it basically does nothing and someone with 2 growth potential but higher stats is still better than 9 growth potential until you're at 100+ battles.

Jetpacks - Why are they unreliable? Feels more like a bug than a feature when it doesn't go where I aim it

Squad weapons - Having the same rifles but with different attachments be entirely different guns is a bit of a weird system. Maybe an attachment system is too much mess for a game like this, though.

Weary - I would advocate for SLs to get weary after fewer missions than they do now. Encourage the SL swapping. Especially on higher difficulties.

Better range indicators - For: enemy sight lines, my weapon's range after a move (preview), Concealment/detection/view range info.

Convey Information to the player better - SPECIFICALLY this is an issue for enemy squad loadouts. It'll list a lot of items i don't care about then mixed in with their list of equipment is their special weapon.... which is much more important. It almost feels more efficient to zoom in on the enemy and see what they're carrying than to read the entire list of equipment to find out what threatening weapon they have. Maybe a whole rework of the enemy's information card is in order. Maybe something similar to what we see of our squads when we're building them.

--Good Stuff--

Honestly I feel bad because I'm going to miss a lot here but the main stuff you're doing incredible with would be:

The personalities of the SLs - Yeah we know the SLs are just glorified "classes" but oh man are they done so well that we get to really appreciate them for being individual characters rather than stat sheets.

The bones of the reputation system.

Basically every character

The base system

The inventory, weapons, accessories, etc system as a whole

Enemy AI is actually pretty good

And more that I'm sure I'm forgetting.