Oh yes - I know it's perfectly valid - and I used to do it in the early 80s too... but it won't ever give you a split tone effect - nor will the highlights develop independently from the shadows in each developer... you only need to see the way the characteristic density curve grows through development to see why this is. the highlights grow at a rate proportional to the shadows, just much slower... i.e. 10% growth of both highlights and shadows... I'm glad you're thinking about process like this though. Creativity is good, in my book.