Roof design problem

Dear All,
I have a roofing problem. Roof diagram is below and I'd really appreciate some advice.
v = valley, x = pitch roof apex, l and - are walls, P = problem.
        rear of house     ------------------------x----------     l     v    x     l             l         v    x     l     l         v    x single l     l         v x storey l     l    garage     vx rear     l     lxxxxxxxxxxxxxxxxxxxxxxxx ext.     l         l pitched roof Vx     l     l         V    x     l     l         V    x     l     l         V    x     l     l     V    x     l     l-------------P---------x----------------     l     l        l        l             l flat roof l     OIL    l original    l     l area of l     TANK    l 2-storey    l     l garage l        l part of    l     -------------l     l house     l garage door
I would like to extend the pitch roof along the side of the house to cover the area of the oil tank - this will be a utility room etc.
The problem - the valley (marked in capital 'V') ends below the level of the flat part of the garage roof, at point P.
Solution: 1. rotate valley 'V' (pivoting where it meets roof ridge) up. 2. build approx. 2 brick high wall on top of garage wall (on the rhs of the flat part of garage roof) to support new wall plate. 3. extend wall plate to meet new location of valley.
Sorry, it may be rather meaningless unless you can see it but thought I'd ask anyway.
If anyone can understand, is this a solution and what may be better designs?
Thank you, Neil

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