Read this a lot and disagree with it every time. Busquets wouldn't be as effective if he were to enlarge his action radius, make himself available all over the pitch and carry the ball with him into the final third. I've seen him do that a couple of times and it looked awkward everytime, most notably against Italy in 2012 there was a funny scene when the game was already won, he drove forward and stumbled over his own feet when he dribbled in the final third. His body stature isn't built for that role. He's best at releasing the ball with one and half touches and transition attacks from deep, not move around with it. The Real Sociedad game should be proof enough for now that it is no solution to move Busquets higher up the pitch.
I'm not saying you're wrong, but you should also consider that watching someone playing in an unfamilar position once or twice will not show you the extend of his potential. If i trust any play to adapt to a new position, it's busquets. He has the required technique and vision, but also the work ethic and ambition to make it happen, even though the transition would probably take half a season.
I still wouldn't approve of him becoming xavi's heir though, because we would lose him as our pivote. you could argue about who is the world's best DM in absolute terms (for me, that's still busi) but for this barca side, for our style of play he is the best, hands down. even if he performs exceptionally as a CM, it would be an overall downgrade i'm afraid