I really like that idea with the yeast. It should create some crazy nice flavors that will go nicely with my malt profile. Where do you think the Ca needs to be? I was thinking about 75mg/L just to stick right in the middle of the range.
75 would be fine. You could get away with as little as 50, but I wouldn't go under that. My Belgian beers have turned out much better with just a little CaCl than trying to replicate any specific Belgian water.
To paraphrase Dr. England - "Off-flavors smooth with time. So do mountains. Brew it right from the start!"