The idea would be that while visiting the Greybeards you come upon an alter. At this alter, the dragonborn has the ability to create their own shouts. Of course your creation would based on the words you have learned and the amount of dragon souls you have available. Perhaps gold would also play a part since I always believe making currency more useful is never a bad thing.
Currently the game game allows for each shout to contain three words, but those words really just enhance the same shout. But at this alter, similar to the spell creation system in Oblivion, you could create a shout with whatever desired effects you wanted.
For example, if you could put the words FEIM + HAAL + YOL together in a single shout you would have a shout that would allow you to be invincible (FEIM), Disarm your opponent (HAAL), and Create fire damage (YOL), all at once. Thus, through this idea, gamers would have the ability to create their own shouts, and tailor them to the skills they wish to use.
Any thoughts to doing something like this?