I don't see any reason to change the drivetrain at all, maybe get a different cassette when the current one wears out.

May also want different pedals more appropriate for whatever shoes you want to wear.

I had Serfas tires on my MTB commuter but I have Kwest on my current fixie commuter - both great tires. Some tires have a casing that deteriorates with typical commuting use... Performance's house brand is like that... total junk.

I never liked suspension forks for road riding either but maybe if you can make them really stiff they won't bother you.

So I suggest: 1) lights 2) slicks 3) fenders