So I was thinking about ways to make a 10 gallon batch of lager that dont involve buying 4 packs of wyeast and making several starters. I came up with the idea of brewing a table strength 5-6% bier de garde(10 gal.) with wyeast bohemian lager, and then washing the yeast and using in a northern german pils. That way I buy 2 packs of yeast and make a 2 l starter on the stir plate and split it between 2 fermenters at pitching. Anything wrong with propagating at 60 in a bier de garde and then reusing to do a standard lager?

No problem at all. I use that same strain for my "blond ales" during the summer here. It takes too much time and effort to chill to lager pitching temps when it's 100°F outside, so I ferment at 62°F and call it a blond ale.