Because that went so well when Bethesda started something like that?This is a straw man - no one claims this but you. Modding is equivalent to a substantial part of game development, namely everything above engine level or whatever area is open for modding.
The legal issues are easy. TW negotiates a payment with a modding team or an individual and that's it. The problem is that they are not that interested in improving their game and hate to work with external devs.
I gave you several sources to back up my claim - not my fault if you don't want to read them. If TW want modders in the team - they should hire them as professionals. Not just buy out mods...
Regardless isn't one of the dev's literally one of the Floris modders?
Anyway in summary: Taleworlds need to fix their game - as simple as that.