Can you wait? On deck (in about 10 days) is a Old Ale using 1469
I have a Timothy Taylor clone (OG 1.043) currently bubbling away with this yeast, I thought it would make the perfect base for a Old Ale. I even went out and got a can of Black Treacle.
My experience with brew big beers on the prior yeast cake is that the alcohol tolerance levels Wyeast quotes are pretty darn close to real world yeast behavior. So, I would be worried that the 1469 would give out too early for a 12% beer. But, wow, the Wy description of "full chewy malt flavor" sounds very enticing for a big beer....