You have a couple of problems that you’d need to overcome when it comes to HW mods. More so than something like Skyrim actually. First off the majority of the big mods are ALL using IP from other games and the only reason why they are even allowed to exist is, of course, because no money is made off of them. Heck even the mods that kitbashes HW mods have issues with trying to make money of them since those models are not free to use. The engine of HW1:C might be open source but you still need the dat files (that includes the models) that are on a HW CD that is bound by DRM (theoretically) and thus is IP that you can no sell.
Imagine a mod that is being sold that contains 99% original models and work and a month later is is discovered it contains a badge that happens to look like a rebel alliance icon. Bam, take down notice, lawers, refunds, etc.
Honestly there were far more issues than simply the paying for mods like QA, expecting the community to police the mods, IP issues, theft, Quality, support (from both modder and developer), the actual split of the money, abuse by fly by night operations, etc. It’s also come to light that (apparently) valve/beth straight up stole the idea, and then decided to rip modders off, from another site. Do some research regarding it.
Yes I can see how a modder can get excited by the prospect of making money off of their passion/hobby. But this is an extremely complex subculture that exists ONLY because mods have never been sold. There is a long history of DMCA’s, cease and desists, etc. despite no profit being made form these mods. You not only have to overcome the history of companies resisting modding at first (quite aggressively iirc) but also the fact that they have always been free. Why do companies and modders now suddenly have the right to extort money for something that has always been free?
Basicallly Modding needs to change almost completely before you can ask money for them. Then it is no longer a hobby or passion but a job. You are then nothing more than unpaid contractors of company X creating free DLC for them that they then take 75% of the proceeds despite them literally not putting in a single minute of support or work. In what word is that right?