Rent control isn't the fundamental cause of high housing costs: it's mostly a matter of supply and demand. And, yes, rent control limits supply a bit, but nowhere near as much as complicated, arcane, and expensive building and zoning codes.
Given the trade offs, the only reforms I'd make to rent control is having some kind of gradual income requirements. The higher your income, the less rent control you get, up to the point (say, $100k+) where you aren't protected by it at all. Even that is mostly for optics, though, and wouldn't help housing costs too much.