Here's a picture of my brand new 500GB SSD and the adapters:
It sits very firmly.
I've found the routine which is responsible for calculating the memory size. It's only a single address that gets read. I will use a simple compare which will display the correct amount. When it can't count it fully, it'll display 8192MB instead of 0. Writing the code is easy, but I don't know yet how to insert my own code into the BIOS.
I've found all kinds of different mPCIe cards. There's a card which can be used to decode all video formats in 1080p. It's only 15 Euros and would make a great video player out of this little router. I've also found an expander which supports connecting up to 4 mPCIe cards. I hope the sample I'm trying to get is not too expensive.