It is a great camera. I actually bought the S1 in preference to the S5 as I wanted the more solid build, plus full sized HDMI and top screen display.
One of the autofocus features I use the most is the tap to focus (can't remember exactly what is called). I recently filmed in a factory using a crane, so had my phone running Lumix sync via WiFi, and then was able to set a focus box and tap on my phone screen to set the focus area.
It worked flawlessly, plus the ability to also remotely set iso, white balance, shutter speed and aperture was amazing.
The fact it takes fantastic photos is a bonus too.
I do agree with you about the limited lens options. However their quality is stunning, and if you're going to stick with the system then the investment makes sense.
I hope you get the opportunity to do some travel videography 👍 and thanks for taking the time to write up your experiences.