Mining nodes are all already in data centres. We are already far past this point, so I would not consider that to be a good reason not to increase the blocksize. Miners can not "raise the fee" they simply just choose what transactions to include and not to include, collectively this creates a free market for fees. With an arbitrarily small block size limit it has more in common with a centrally planned economy.
This is back to Peter Todd's famous question: If it is already centralized then why make it worse
The relay network that miners are using right now are a perfect example of now we are relying on private company to provide the bitcoin network necessary service. Following this route, in future all the mining nodes will operate on a private company's network, so that a couple of phone call can shut them down right away
Small block size does not preventing you from inventing fee-free transaction services off-chain. In fact, limited at 1MB or limited at 8MB is the same effect
because bitcoin is never going to scale indefinitely. So, if you sooner or later have to limit the block size, then why not do it now when bitcoin core software is still relatively light weight. It is the direction that matters, not parameters
You can be damn sure if this private company started doing something the miners didn't like it would be replaced, probably within one or two days. As I understand it, the code is all open source and it's just a matter of running similar code at new data centers and then reconfiguring some IP addresses in .conf files.