Your best bet is tomorrow to call our forum member Eric at ADK to see if he can make your dream possible. I am a recent strong advocate of laptop HD video editing but 4K is out of my league. In commercial off-the-shelf products you are limited to 4-core processors which might be the bottleneck. We have some 4k material in our PPBM benchmark and a few of us laptop owners have been able to get some decent scores on that timeline You definitely need Premiere 8 and you might need dual mobile GPU's to help with that 4k material. You will be looking at dual SSD drives.
The stuff on his site is crazy.
I don't know anywhere else in the world where you can find a laptop with 4 internal hdds!
Can we please ask him to provide some feedback and advice?
Just call (if possible) or use the contact button to send an email. A good number of forum members have dealt with ADK and have been 100% satisfied with the results and the provided tech support is excellent. Eric can ask all the right questions about your workflow and the input and output requirements. If you go to our Premiere Pro BenchMark (PPBM) web site and log in you can see 184 tested results with the benchmark (only 7 laptops). But there are a good many ADK tested machines listed.
The Clevo shells we use have 2 M-Sata slots normally. 1 you want to use for the OS and the other you can use for a cache drive. The new Clevo shell which is our 9500Z also uses desktop CPU's instead of a mobile which means you can have a 4790K which would far outperform any of the mobile CPU's for 4K. The media drive may need to be an SSD as well depending on the 4K media your using. The GH4 media can run from a mechanical drive but only a few layers so your editing workflow will decide whether an SSD is a better idea for media.