Going full capitalism. I.e:
Investment: You sponsor another player for xx number of rounds with yy amount of money, resulting in yy/total value amount if shares in that player. The affected player can offer to buy back their shares early or pay a fixed amount with interest (like a loan) at the end of the xx rounds. If multiple players do this and collectively have a controlling share of a player, they get to choose what that player does every other round. Including selling off property or using kept cards.
Theft: like the official 'break the rules' version, you can physically steal from other players/the bank. If by the end of your next round no one has called you out, you announced it and can get away with it. Otherwise straight to jail and triple the value of what you stole goes to whoever caught you.
Slums: in exchange for reducing rent owed to you by another player, you can take one of their next dice rolls and add it to your own in your following round, or just trade movement for rent in general i.e. they can't move their next round in exchange for not paying you rent.
Privately owned utilities: if you own both the utilities you can take a percentage of all rent paid at any point, instead of the rent on landing on the utility.
Just for fun, three card draw: if you land on chance or community chest you can pay an extra two hundred to the bank to pick two additional cards. But you must play or keep all cards.
There was a shitty f2p MMO called GunZ online once upon a time. It was so badly programmed that glitches literally became the primary gameplay loop.
I loved it. For those few that could get into it, it was a unique heaven of fps and fighting game that filled a void an over caffeinated teen with nothing but hyper focus and time didn't know they had.
Also just ridiculously horny people.