A third Highlander movie simply takes place before Highlander 2 in order to avoid it entirely.
It gives the immortals an origin story so bad that decades before the Snyder Cut, an alternate Renegade Version was released years later to try and undo as much of it as possible.
Much like the Snyder Cut, this version tries to built a very different story out of an existing movie.
It improves some of the plot details, but nothing short of an entirely new film could have made Highlander 2 work.