If you use masonry paint, we could head in a warm greige direction for all of it - not so yellow . .. something that can give you a bit more contrast against the white windows and trim - even 40 does a lot for us . . . what about a blue green gray? You will get a coastal / mod vibe and it will relate to the farmhouse look .. .above bm silver mink http://www.benjaminmoore.com/en-us/paint-color/silvermink and below . . . gilbraltar cliffs . . http://www.benjaminmoore.com/en-us/paint-color/gibraltarcliffs Shingle look siding on the side dormers would be neat to get that cottage mod. . . you can stick with yellow but I don't think it complements the roof tone. With the blue-green grays, the white windows and trim will really pop beautifully. . . You can also go more neutral with a warm gray - greige . . . here's the siding tone http://www.benjaminmoore.com/en-us/paint-color/capemaycobblestone paired with this for brick - http://www.benjaminmoore.com/en-us/paint-color/graystone potential future red windows . . .aluminum pits over time, so if you have just one side you want to try, you don't have to powder coat, you can take a small brush and just do them by hand with latex paint if they are 10 yrs old or more. . . one advantage to gray . . future see [houzz=]

Treating the sliding doors as a modern insertion and keeping the rest traditional could be striking. However, what does the house need from the interior? If it needs more light/views opening the house further with larger windows could be great too. An important detail for the sliding doors will be the casing (trim) - whether modern and intentionally different or matching the rest.

No your roof can't support that weight, it's designed to hold the weight of shingles only. You will need to contact a structural engineer to come up with a plan to support the additional load.

Pictures would help...are you planning on getting a new roof or is it staying? If it's staying, is it tile, shingle, metal? And what region is it located?