Hmmm... Some interesting ideas.
I like the blonde ale idea. I don't have great temperature control, and I'll just be depending on a big water bath and average min-max temps of about 8-14 May-September. Doing an Ale as a starter would mean I could get started in April, before it's really lager time.
Regarding Bock and Maibock, I'd always thought that yeast from anything over about a 1.050 beer would be too "stressed" to re-use. But then I was just listening to a podcast about High Gravity brewing, and they suggested using a high-ish gravity wort in a starter for a high grav beer. So maybe by brewing something in the 1.070 range I'd be breeding yeast that would be better equipped to handle the 1.10 or so of the doppel?
Lots of interesting ideas here