Working on a 24XX-based wargame

You can see a copy of the 24XX basic rules at https://24xx-srd.carrd.co/#rules.

I'm thinking of adapting them to a war game where each unit has different skills that you roll depending on the unit's tactic for its turn. It could be collaborative against a referee force (player facing rolls only, like regular 24XX), or competitive (each player rolls on their turn).

Casualties inflicted and risked would be some fraction of the force inflicting the casualty, probably 1/4 for easy calculations and fast play.

I'll post more as I progress with the game design.

Thinking, more specifically, right now, about formations and how they affect movement and combat.

Basic formations would be Tight and Loose. Tight makes the unit move normal speed, hit hard in melee, and more vulnerable to artillery. Loose moves faster over open ground, but can't take advantage of roads. Doesn't hit as hard in melee, no effect on shooting, less vulnerable to artillery.

Changing formation would be a turn. Moving would be a turn. Attacking would be a turn. Regrouping (to shed a "hindrance" from combat losses) would be a turn.

Maybe roll morale to regroup; on (1-2), they flee.

Skills?

Movement (changing formation, moving)
Melee
Missiles
Morale (regrouping)

# Missiles
- (5+) inflict 1/4 strength in casualties
- (3-4) inflict 1/8 strength in casualties

# Melee
- (3+) inflict 1/4 strength in casualties
- (4-) suffer 1/4 opponent's strength in casualties

# Morale
- (5+) regroup: clear hindrance
- (3-4) fail to regroup: still hindered
- (2-) flee

# Movement
- (3+) move up to full distance
- (4-) hindered in next action

# Material (bonus skill for battalion scale - would like an "M" word for this)
- (5+) act normally
- (3-4) hindered on this turn
- (2-) cannot act on this turn

# Missiles (player-facing when attacked)

(5+) no casualties

(3-4) suffer 1/8 attacker's strength in casualties

(2-) suffer additional 1/8 attacker's strength in casualties, and hindered

Those are interesting. Did you test them in actual gameplay?
Do you know (Advanced) Song of Blades and Heroes rulesets? - they may provide what you are looking for.
Other then that: interesting concept.

I need to get into VTT before I will be able to test in a game. The learning step for using VTT is too high for me.

If you would be interested in playtesting rules like these, I have a more recent version that I would be glad to share with you.

To be honest I won't have time for such test - and even proper group. I just like to theorize about games rules...:) And I have read a LOT of them. I like to think that I usually can simulate gameplay in my brain after reading rules... but probably it is not necessary always true:) Did you try https://www.owlbear.rodeo/ ? It seems easier to me, but I haven't tried it to any bigger extend. If I were to be of any help to you with those rules - only thing I would able to do is some async(one move per day) plays with you. But I'm more interested in skirmish scale battles, and those rules seem to be for more for units?
Also: for a long time now I'm thinking about mixing some RPG ruleset with some skirmish war-game rules. As to have nice narrative options and fluid, very good battles. Now I'm thinking to about combining Stargrave with Ironsworn: Starforged - seems good fit. But I think I will start new thread here when I will be ready for more work.
Good luck with your project!