This video was mde before chain signals existed :)
Either way, by upgrading I also meant having more than two lines. It's a bottleneck in the design with just one way in and one way out.

The second weekness could be solved by placing the chain signals - that way the train will never enter crossing where both lines are occupied, but would rather wait outside the crossing for the first available line. (well it works for three platform in 100%, so I pressume that while being more complex, principally it should work for this one too).