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.

Your deck will be amazing. It has fantastic form and plenty of architectural interest, it will add enormous benefit to the front facade and street appeal. I love your palette, it is simple and still has point sof interest. MY suggestion would be to use a combination of your exterior colours applied where best to highlight the deck structure and either tie in, or accent against it. Ding all of these things by painting the lower retaining section in the base grey the charcoal colour to continue and blend into the lower floor brickwork, also do this charcoal on the upper deck frame which is also the roof of that entry way. I am trying to say that thick timber which trims the deck. And the slatted section of the stair wall which acts as a breezeway in the light grey- why? Because the open sections of the slats will always appear black as you can see through them to under the satirs, and the light grey slats will stand out and feature that shadow line, perhaps even use liting to further enhance this detail. Lastly, the stair treads themselves left natural, like an architectural contemporRy stAtement, the natural timber tones will be rich and sophisticated and act as art inviting you to the home. These stairs would really pop and be commentedon at street level, also consider lights in each tread, perhaps the slatted wall side to highlight both this and the stirs for night practicality. What a stunning entrance. The natural character in rich timber tones will warm the grey, keep it contemporary and not introduce personalized colour, which can take away from street appeal. This on the other hand, appeals to everyone. And greenery, landscaping will only take this to the next level. Literally!

Lighting - pendants over the servery bench should be another feature that complements your chosen kitchen surfaces. So whilst I love the copper pendants in picture 1.. They could work depending on the rest of your decor and would be a highlight in a neutral white/timber kitchen = Good! If you choose copper you would complement it with a couple of copper bench top items. These are beautiful! (I collect copper because I love it, my kitchen pendants are silver, I renovated to sell in the next 3-5 years) You will see a picture starting to form in your mind and there is nothing wrong with making a statement with your lighting. I found that when I wasn't sure I would get a very strong sense of what was right and what was wrong for a space, then common sense or passion would determine the outcome! Here are another couple that might work, look her on Houzz under lighting, search pendants, then have fun looking!Timber tones with black or white to complement your cabinets... or Statement white pendants for a bit of quirky fun! Your personality can be reflected in your lighting and accessories creating that point of difference from the predictable white on timber look. Plus don't forget the power of greenery to punctuate the theme!

It's great to see professionals consider sustainable options