I know of no reason to not do this. Get a spec sheet on the toilet, and get out your geometry book! You need to VERY carefully plan the rough in on this one, or you will be in big trouble. Personally, If I was going to do this, I would get the actual toilet and create a full size template on a piece of 1/8 luan. Use T-squares to line things up and verify wall clearances and determine your rough. Make sure to include finished wall thicknesses in your planning.
There will be dead space behind the tank You could build a little corner shelf there to hold a plant or something.