I would change the derailleurs. I'm not a big fan of derailleurs to begin with, and if you factor in Tiagra it's just a recipe for frustration, IMHO.

I would put on XT or 105, depending on your intended use. I like XT, so that's the route I would go.

The wheels don't bug me that much, but I'd add fenders, a rack and a Brooks. I'd probably also change the handlebar, but barcons don't bug me so it would be money I'd rather put into other things to change that.

I've been considering a Cross Check build. I have extra MTB parts...XT derailleurs, WTB hubs, XT crank and BB but I'd still need brakes, headset, stem and bar, rims and shifters (plus all new cables, of course). As soon as I have the cashola that's probably what I'll put together for my all the time bike.