Now is actually the ideal time to transplant most plants. Plants are starting to prepare for dormancy but have time to adjust to their new location so they can settle into their new holes. There are some Encore Azaleas that could easily fit your needs. Sun tolerant, repeat blooming, and hardy through Z6 and meet your size requirements. I know there are some dwarf lilacs around also that could be a good match, though I would probably use it more as a side anchor plant than under the window. I think most of the dwarfs are around 5'. Hydrangeas and viburnum could also be good picks. Most hybrid tea roses would fit in that space also. They really are not as much work as most people make it sound. Just remove spent flowers once a month. At least not in my area. You have enough space there I would definitely recommend doing shrubs then a front layer of shorter plants. Maybe some sweet william/dianthus, sweet violet or a daylily.

If you don't need space for socializing on the deck, I think you would be better served by a simple, 6' wide runway deck/walk that hugs the house and then devote the leftover space to planting. Split the steps with half at the deck and half at the entrance to the walk (from the drive.) It would seem a lot more luxurious to you if you made the step-treads 16" (front-to-back depth.) Use a conventional railing instead of seating. (You can't post photos by embedding code, but you can upload them directly from your computer by using the "Photo" button at the bottom of the window where you create the post.)

Thank you everyone for your input - some great info here for me to consider. As I have been researching landscape professionals, I have been concentrating on those who seem to have significant hardscaping experience, since I know our project is going to involve a new retaining wall and section of patio at a minimum, and possibly much more. Someone to help me choose plants and design plantings is a secondary concern, although I have certainly been paying attention to people's styles in that regard as I research. Anyway, the people I have emailed thus far are all design-build firms, which I assume will be the easiest way to deal with this project, especially given Revolutionary's note about not building what other people design. That is understandable and I'm sure most of these designers have a team of masons/contractors they work with to avoid that exact issue. It sounds as though paying a designer for a buildable set of plans to shop around to contractors will just end up costing a lot more in the end, for very little benefit - that is, as long as I can find a design-build firm where both the designer and builders are equally talented! Asking whether these designers are willing to chat on the phone first is a terrific idea - I will absolutely ask! Site consultations have been offered at anywhere from $200 for one hour to $375 for three hours, and while I don't find those fees outrageous for someone's expertise, I really don't want to agree to the fee only to find that I can't stand someone the moment I meet them, LOL.

As I despise black trim my suggestion is monochromatic. Paint all trim, siding and the bay window area including garage door. and front door sidelight the light gray (middle one of your 3 samples). Paint the door and shutters and very dark charcoal gray. Your house does not need to be outlined in black. Then the landscaping needs to be improved