Those are all great points, but IMO not really that difficult to handle.
> If the company spins-off a segment
A spinoff is just a divided in the form of stock in the new segment. This is easy to handle. The short is now simply short both one share of the original and one share of the spinoff. The long now owns synthetic shares in both.
> If someone wants to acquire the company
An acquisition is just a one-time terminal dividend to the company. In a cash acquisition the short owes the long the value paid for the stock. In a stock acquisition the short is now short the equivalent shares of the acquiring company.
> Shares can vote, your stream of dividends cannot vote.
This is the biggest wrinkle. But it basically still exists even in the current system. If a stock has short interest of 50%, then there's 150 shares held long for every 100 shares of float. In practice it's not really that big a deal because 99% of investors just vote the proxy.
At voting time, some investors will find they own synthetics and some will find they own originals. Just the same as today some will find their stocks on loan, and they can't vote. It doesn't really seem to make a difference.
IMO I think a requirement for public listing should be letting all beneficial owners, including those who own synthetic shares/have shares on loan. I think if anything it strengthens corporate governance, by avoiding voting rights shenanigans. The two classes have equal interest in setting the company perform well.