One day I will be Ultrman.
Now this is a reissue I'm interested in.
Not that I can afford the dang thing.
If I were in your shoes, I'd probably go with the camera. Yes, lenses tend to be a better long term investment, but it sounds like a GH5 would be really helpful for your work. Even cheaper EF primes like you're using can produce excellent images, and the features and reliability of a GH5 will help a ton and last a very long time.
I agree with Matthias though. It might be worth looking for cheaper/used lenses to fill out your range a little.
I'm usually cynical about these kinds of lists, but I dig the range. It's refreshing. Early cinematographers deserve more love, even when their style doesn't align with modern sensibilities, and Kazuo Miyagawa should be a household name (well, amongst movie geeks).
But, of course, the exclusion of Gordon Willis is delusional.
Every Frame a Painting's video on Jackie Chan also touches on a lot of these points, and some additional directorial technique. It's essential viewing for action filmmakers/fans.
I guess the question I'm really asking is, does anyone know what the actual resolution of 4:3 4k mode is? Is it vertically the same as 16:9? And is there a difference in crop factor? Are there any advantages to actually shooting 4:3?
I'm guessing some marketing person came up with that because there's some shots of people with phones.