Well, you can use git just as you normally would, nothing stopping you from using that. Just make sure you exclude the right directories so you don't deploy your local wp-content to prod. I don't really know of any wordpress & git gotchas.
Bootstrap, CSS preprocessors, mobile first, that's all dependant on your theme. I've seen some pretty decent setups that incorporate a router similar to what Wordless is doing. CSS/Less/Coffeescript, you can set up a grunt config to handle all that easily enough, nothing in Wordpress will prevent you from doing this. You should incorporate your CSS/JS with the usual WP include functions so that WP Total Cache and similar can cache it properly, but there's nothing really weird going on there.
So, now you've got grunt linting your JS like a boss, you've nice theme partials, you've got some custom libs that functions.php is bootstraping for you, your theme folder has morphed into its own MVC architecture.
There are a _lot_ of shops out there that pump out WP site after WP site. I have to think that a well constructed starter theme that incorporates more modern workflow ideas would go over well, but at the end of the day you're still building on top of wordpress. Whatever starterkit you use is still limited by the parent it lives in.
To my knowledge the most painful part of WP -- keeping the options data in sync between dev, stage, and prod all the while you add and remove plugins -- is still largely unsolved.
