Here's some information about sliding windows. In a storm the exposed track fills with water and if it doesn't drain fast enough water enters the house. I've seen it happen in a test chamber. The fact that they are cheap is not enough of a reason to put them in a house. And little burgers are known to cause indigestion. Life is not fair.

The second floor plan for the bonus room shows "pony walls" along the two sides with the rake roof, but we don't know the plate height of those walls. But it's this technique which allows the exterior elevations to be as they are shown, and much better appearance for the garage/bonus room exterior massing. As for the garage gables, the shed-type dormer allows for wider dormers (and more interior usable space) than a gable-type dormer. But if that shape is appealing, and a smaller interior space is workable, then go for it! Beauty is in the eye of the beholder, but if it was my house I'd stick with the original elevations. Good luck on your project!

I see your photo just fine. What strikes me first about the house are the landscape timber flower beds sloping to each side. I would start by removing all of the timber, and saving all pieces that are in good shape to be reused. Pour a solid slab in front of the entire porch to visually open up the approach to the front door. Rebuild the flower beds on either side of the porch so the tops are level. You may need to stairstep beds on the right side. Replant the existing plants or put in new plants. Below I show the left half of the house with this scheme. While the shutters on the left window are appropriately sized for the window, those on the right are too narrow, but there is no way to add larger shutters. I wonder if that double window bumpout (?) would not look better if it were painted to blend into the brickwork. Overall, however, I like the way this house looks.

If you need new paint, I would leave the brick unpainted, paint the siding a navy-ish color (like hale navy from BM), paint the door red, and remove the shutters. And then landscape. BUT - if the paint is fine yet and you simply want a color change, first do the landscape first. I think you'll be amazed at the change in curb appeal you'll get...