I recently ordered the Mercier Kilo WT and am going to take it to my LBS to be built and tuned, i am going to ask them for the best upgrades off the bat but does anyone have any suggestions before I do so on tires, hubs, cogs, etc??

I'd just ride it and replace parts as needed. The kilo WT is pretty bombproof out the box, more so when professionally assembled.

You don't want to get to the point where you realize you should've bought a surly or all city from the getgo.

The only parts that needed replacement on mine were the tires, pedals and saddle. I also changed the handlebar, brake levers and stem for fitment reasons, and lowered the gearing with a larger cog. The wheels and crankset are excellent quality and should never need replacement.

+1 on gear ratio. I just bought one too with the intention of setting it up as a winter bike. I'm taking it from 48x16 to 44x20. I'm also throwing on a set of Sugino 75 crank arms and I'm replacing the bottom bracket. Plus snow tires, wide risers for handling, and I may or may not also swap the saddle.

The problem with the WT is it's set up similarly to the TT pro when really they're two different bikes. I guess that's okay 6 or 9 months out of the year when you're riding around in favorable conditions. But the WT has a lot of potential to take you places that the TT just won't go.

I bought mine as a frameset so no comment on stock parts.
I am running Schwalbe Little Big Bens (40mm) with fenders.
I really enjoy riding mine and hope you enjoy yours a much.