PC is open indeed, but for the love of me I can't remember the last time I've actually upgraded a PC. I usually buy a upper mid-range to lower high end PC (currently running Core I7 5820K, 980) but i actually very rare upgrade them. The ones I buy last me for the 2-3 years of which ever games i play at the time, when i can no longer play them at the graphical level i deem acceptable i buy a new one.
And this is because the upgradeability of most PC's is sort of a myth, if you buy a hardware which is all of the same range when you'll have to upgrade a component the rest will become a bottle neck.
And i don't see this being any different, the added cost of the router and the entire protocol simply writes off the benefits considering that an upgrade will require you to upgrade at least 3 major parts.
On top of that you run the risk of the "router" most likely be turned incompatible within a few years simply because the standard will evolve to allow for additional bandwidth, different power requirements, an improved form factor etc.
Take a look at PCI express for example from version 1 to 4 there were huge changes in bandwidth and power supply, and while some hardware kept backwards compatibility it was in most cases severely hindered by the bandwidth limitations. Put in a modern PCIE 3/4 graphics card in a PCI 1 or even 2 slot and you'll see the difference high end cards lose upto 75% of their performance, some wont work at all due to the power supply differences.
Do you really think that for some reason that protocol would be exempt of that?
We already have a combined creativity of a multi-vendor environment, open your phone it has components from a 100 vendors. There are memory vendors, SOC vendors, sensor vendors, radio vendors, screen cameras etc. You can have an LG phone with a top of the line Sony camera, and NVIDIA SOC and a Samsung memory in it, do you really need to add a plastic square that says Dr Dre to it?
Not to mention that at least now you have the ability to debug issues with fair ease, if the PC over the past 40 years have not managed to tackle cross vendor compatibility even at a hardware level (just check the accepted hardware list for your mother board for example) not to mention on the software level what makes you so sure that this all of a sudden will?
I would rather much see an easy way to connect peripheral discrete devices to my phone with ease for the extremely rare occasion i would (and atm i can't think of one) need it than to have to select different hardware for my phone hoping it will all work together than having 6 different vendors to get support and claim warranty from while hoping that at least 2 or 3 of my lovely blocks will be compatible with the next years model.