If we are being realistic about the video issues, the problem lies in the unpredictability of the higher end modes. They work... but with too many different caveats. From a cold start, we can expect 8K30p, 4K60, Oversampled 4K30 & 4K120 to work anywhere from 15-30 minutes. In real world use though, it is very rare that we will be using the high end modes right off the bat.
You would expect to turn on the camera, shoot some photos, shoot some normal videos, and then you may decide to use one of the better quality modes. The issue is by spending some time in these non-critical modes, you eat up available resources so when it's time to use 8K or 4K120, at that point the camera may already be indicating that the available run time is shorter, and even worse, it may already indicate that the camera is too hot to operate in these modes. Imagine shooting a wedding reception and filming at a reasonable 4K24p... then an important part, like cake cutting, or a speech or something starts, I would want to switch to a higher quality mode to film this brief event... but, you might not be able to do that. That is painfully unreliable for client work. There's no waiting around to cool down, or re-takes in a scenario like this. There are only two ways to deal with this. Either 1) Be relegated to the fact that you will be topping out at 4K24p normal mode or 2) You will need additional gear. Either a second body that stays cold until its time for these high end shots or an external recorder, which would top out at 4K60. (Oversampled 4K would actually still overheat.)
As it is, the Camera will be fine if you can accept 4K30/24 in non oversampled mode. This is a step up for most Canon users anyway, since we are used to filming in FHD or 4K with a crop on an EOS R, 5DMkIV etc... Also, an external recorder like the Atomos Ninja V is a viable option as it allows up to 4K60p pretty much without limitation. (Again HQ 4K will overheat). But if you have any plans to use 8K, 4K120 or 4K Oversampled... it will require forethought and planning, because you may not be able to use these modes at any given time.
What can be done? I really doubt that there is a physical fix that is economically feasible for Canon. That leaves a firmware fix. In order to make this a success, we need reliable access to the higher end modes even after moderate use. I want to be able to shoot lower end modes and stills and know that once I switch it to 8K or 4K120 I can have 15 minutes of usage time no matter what. This might mean taking the limiter off it when I say I need it and accepting any consequences that may come with it. It's the same as running a car at redline. I won't always do it, but when I want or need to use it, let me do it. Hopefully it isn't that extreme and here's hoping that Canon was super conservative in the implementation of the automatic shut downs in overheated modes, and there is some room for dialing it back.
