Sister of Battle are fanatical followers of the emperor and he said "Give the Land Raiders to Custodes and Space Marines". So even if they were gifted a Land Raider they wouldn't use it.
Lore and gameplay often clash with each other. I focus on gameplay and try to stay lore friendly. But when adding these units I looked at what the Sisters were missing and a late game transport vehicle just fit them greatly.

a rhino would be more lore friendly for the sisters. interesting stuff though

There is no reason why a Sisters cloister would not use a land raider, especially if it was gifted to them or they recovered it.

Faith and Fire by James Swallow has several sisters superior working together to deal with a rogue governor, so there is no reason why they cannot band together and form an elite squad

10/10 mod the Sisters needed more unit diversity

I'm not the most well versed when it comes to the lore. But I know that lore-wise at some point the emperor recalled all land raiders and gave them to the marines and custodes before he fused with the throne and no one decided to overwrite this order. Something Guillaume could easily do at any point in time.

I had to look up what a repressor is, essentially a modified rhino. I choose the land raider as a unit because it is a late-game transporter and that is what I wanted and fit gameplay wise.

Sister Superior is a rank in the hierachy of the sisters akin to other military ranks. I know that on the tabletop they are leaders of a squad instead of individual characters, but from a lore perspective nothing would stop the leaders of several squads to band together to form an elite unit, which the modded unit pretty much is and is supposed to be.

I'm a casual 40k fan and I try to make mods that feel reasonable from a lore perspective to a casual fan such as myself and also fit into the gameplay of gladius.

There will always be issues for more hardcore 40k fans when it comes to the lore, but those are not my concern.

I have a couple issues with this mod, mostly because it doesn't fit lore.
- SoB have never in canon used a Landraider. Those are exclusive to Custodes and Astartes.
- A Sister/Dominion Superior is not an individual unit nor a named character. They are the individual leading a squad and a member of said squad, so why are they an individual unit?

I understand everyone has their own desires when it comes to mods with this game, and this is simply my input.

I like the concept of the mod, and I'd ask this: Give us a Repressor and with it, the ability to roll over infantry like the AM's Tank Commander can.
All the other units are great and fit well into the lore, and are fun to use. Great job on the mod, truly