Comment by BobaFloutist

You could have a system that limits sale of IP to clearly defined capitalization, I.E. instead of "You own this IP for 20 years and get x% of profits in return for funding/publishing and giving my y% of profits" it could be "In return for funding/publishing in the next 5 years, you get x% of profits and I get y% of profits, but I still own my IP and your rights expire after a short period of not publishing.

AFAIK that's actually standard for writers: publishers usually license the IP for a period for a prescribed royalty blend and for publishing, and after a certain amount of time or if they don't publish the rights revert, and international/audio/digital rights are negotiated separately.

There's an argument for "What if I don't want to deal with capitalizing on this whatsoever and just want to sell it for a cash payment now because I literally don't want that to be my job," but even then there should probably be a minimum royalty along with the lump sum to protect against exploitation.