Are you going to primary for 8 months? It would probably be fine but I think moving it to secondary after a month or so is advisable. Then again I've never actually brewed a lambic before, only researched it.
I don't think what you're proposing is weird, other than the fact that I think you should pitch some other bugs rather than a standard strain of yeast. Maybe the dregs from a favorite sour of your's or something.