Being a bloodmaker would be nice though your healing abilities tend to make you more reckless. Being able to store memories would be really useful as well. And sense we really know so little about nicrosil compounding that would interesting as well... I would like to compound but Brandon hasn't revealed much specific detail on that. I'm a traceuse so the steel and agility ones appeal to me. Zinc compounding is really appealing as well. My answer would be harmonium compounding. Though that doesn't really count so I think I would like to be a Bloodmaker-Coinshot.
And also is there a term for someone who has all of the ferumchemical abilities?