Yes, centralised. That's the model that works for software development. Where would this voting nonsense end? The alternative is to make development "equal opportunities", anyone and everyone gets a turn at designing and patching! Have fun with the coin you end up with using that development model 
No, you're free to operate and mine on whatever client you want. If you're forked off the network, it's your fault.
Anyway, I don't see BIP103 in the list on the site linked.