this is a gr8 idea
i don't see why you need to touch the bitcoin protocol tho, all you need is to use it.
make a system where anyone can create their own permine, fixed supply, coins ( shares ), and make it possible to trade these shares for BTC in a decentralized trustless manner, you do not need anyones permission to use the blockchain, you do not need anyone permission to innovate.
If you had the skills you could make some money designing specialty coins for this purpose. It would also democratize investing a lot more.