Addition on a side of a house with a valley

[James Edwards]

Investigating the potential of an additional onto a house for the purposes of going from 2 br 1 ba each duplex, to 3 br, 2 bath each duplex.  I've got an approximately 500 sq foot deck that is in the location that would work well for addition, it is around 4 foot above grade, on a valley side of a roof. Top of facia board/end of roof is around 8 foot high from the top of deck. House has basically new metal roof. Deck is basically at the end of its service life. 

I'd like to use this area because it is centralized, deck is gonna need replaced soonish, and 2 walls for the project are already in place. 

More or less the area  looks like this. 

I am trying to figure out how one would tie a new roof into this as the starting point is~ 8 foot. and would be obviously less at the other end. 

I know the ideal answer is to remove the metal roof and re attach up higher, but I would like to avoid that for obvious reasons. 

My ideas at this point are to remove the deck and make the room areas a step down, and recreate the deck later as stairs to access.  However, it still doesn't solve the aspect of how to tie into it, and what the final design may look like. 

Was hoping some more clever minds may have a cool idea here. 

Thanks