Looks like you have several things to consider in the layout. What the view out the window ? Do you really want to see more of whats outside? Cooking is always best on the outside wall to get it vented, island cooking is a last resort, downdraft dont work well at all and the island hood is typically obstructive. Looks like the wall should come out to open the space up. Best advice is to have a designer come to your home and see it in person. There are costs associated with every change and it is very difficult to judge just from photos.The design phase is the most important part of any kitchen remodel the builder is only going to install it as the plans layout. Find a great designer that makes house calls :)

I really don't see an issue with the rooflines. Looks like the angles are fairly similar and the clean lines of both structures should be easy to coordinate, especially in your open, rural setting. Since you've found a stunning deal, I would say, go for it! I definitely would want to find an architect ASAP and by all means, before you pour the slab, make sure you have a plan to coordinate.

We got the IKEA shelves that are pictured in the butlers pantry photo I posted when we were on holiday in Melbourne, Australia. We don't have IKEA here in New Zealand! Hubby is going back over in May/June so will get him to get more of that sort of thing when there. We would pay about 4x the price for that sort of thing here in NZ. I need to work out what I will do now where the fridge was and there is the angle change (does that make sense?).

http://www.houzz.com/professionals/c/new-zealand