After a few moments of trial and error, the mod that was breaking it was none other than Radious. The base TW Millennium mod works fine as does the warband mod, it seems that this is the only one of the mods that conflicts.

@Jensehc
Interesting. I did disable the Warband Upgrade mod in its entirety and the button was still not there but AI was still able to do upgrades. Will try your suggestion later today. Thank you for your help and advice.

@SUNBRO SOLAIRE
This mod and the Warband Upgrade mod are the same mods from before, I have changed nearly nothing so they should still work fine. Try to use them without any other mods and see if they work. This way you can see, if anything else causes the issue.

@jensehc
I do see the button in your screenshots, and I have double checked for it in game. As of now it is missing from my army hotbar. I am using the Warband Upgrade Ultimate with appropriate compatibility mod for TW Millennium and in a past play through many months ago both that mod and this were working in tandem correctly (or at least the original version of this mod from Barackollama) Do you believe this may be a conflicting issue?

@SUNBRO SOLAIRE
As you can see on the screenshots, there is a button when you select one of your troops in your army. This opens the menu where you can select your upgrade.

Not working for me either. The Ai is able to provide upgrades to their troops but I am not seeing any option to do so for my own faction. Any advice or news would be most welcome.

No, AI becomes strongest in this mode.OP

this makes the AI broke by making a basic tier 1 unit's upkeep alot

yeah this isnt working for me either it jsut wont let me even open it in game

@Mad Dog Peter
It works perfectly fine for me. What kind of problems do you have?

pls update, this mod seems to be broken

One step closer to the Morr Brigade's return.

Finally it's back!