I did something similar for a multiplayer RP mod I was making:I can't give the correct answer for this. Because you are asking the wrong question to the wrong person. Creating complex UI that works requires C# knowlage in bannerlord. Probably it has to be built from scratch for mp again. I don't think anyone gonna waste time with it. I have only done basic stuff about UI
Also, I believe the SP gear inventory screen is not a great idea for bannerlord mp. It is time-consuming to select/switch your set.
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Eventually I grew bored of waiting for the custom servers as I'd have to re-do almost everything for multiplayer. But theoretically it is very possible and should be rather easy for someone more experienced than I.