Well I'll be damned, lots of slippery slope type of arguments in here.
Personally, I'd be fine with lootboxes and progression-based skins and custom items for MP in Bannerlord. No serious company would ever cross the line regarding the theme of their games with said items, especially if they are aiming for a highly competitive and invested fanbase. Crossing that line and adding the most ridiculous of things are the modders' job, therefore the casual, "immersion-seeking" players shouldn't worry.
Actually, since I believe I will love this game forever after its release, I would gladly accept (and even maybe take part in) some way of giving TW money after getting my hands on a copy, like buying skins or DLC.