I want to suggest adding Zero's OilRush addon as a type of late game legal activity that requires a lot of capital to start but can pay off big time. I think oil refinement will add a new potential alternative to weed farming but requiring more initial capital and maybe a longer rate of return. So you won't need to worry about cops confiscating your goods but you might need to encourage them to patrol around your refinery as thieves will probably try and steal from you.
I would probably recommend increasing the default prices and returns to make it on par with maximized weed farming but requiring a significant upfront investment (maybe $500k?).
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Edit: Typos and grammar