Hmmm - tricky one. I pondered whether the stock grips could be replaced by the 1150 ones when I was changing my handlebars.
The bars are the same width as the 1150 ones, so theoretically it would work. Unfortunately, the wiring is completely different and there's no way I'd want to retrofit 1150 grips to the 1200.
Some enterprising person with a spare set of 1150 grips handy could have a look-see to determine if the rubber grip part can be removed from the throttle tube. If so, I guess you could swap just the rubber bits. However you'd still have probs with the heated grip connections which go to specific connectors under the tank for the 1150 but are subsumed into a single cable run from the 1200.
This one is rapidly slipping into the "too difficult" section...