The 4 current proposals are:
- Staking key address index
- Ratio delegation stake
- Multi-account support
We won't spend any time digging into each proposal as Sebastien did a really great job describing each in the video. Since he goes deep into the implementation as well as the pros and cons, and even the UX (User Experience) we wouldn't want to do him or you any disservice in this case by trying to summarize and simplify it any further.
Feel free to comment and ask questions. We love to participate in discussions about technical implementations.