You've accomplished wonders in improving your cottage--which is adorable! Even though the photoshopped windowbox is cute, I think your windows are large and low enough that it really would look just as good IMHO to just add some taller plantings below. I think some tall delphiniums with a deep bluish-purple bloom would really go nicely with your pink flowers and would come back each year. Your yard is really lovely already! If you decide to do shutters, I think a dark charcoal or black would look nice, although michelle's dusty red ones are perfect for her garden shed. One thing I've found on GW is that some on here feel that shutters should actually be large enough to cover the windows (if closed), so your space wouldn't meet that criteria. (Mine don't either, but I have them and like mine.) For the foundation and chimney, I'd paint that either the same color as the house, or a slightly darker shade. Your plantings will show up nicely against that. And for the front door --I vote for dark red since I can't quite picture the blue, but once I saw it, might love it as well. Your home looks so inviting.

(not a pro) It might help others help you if you also post some pics of what "rustic charm" looks like to you. But 2 cents from a non-pro until some pros chime in: I love the look of a sage green cabin I prefer your exteriors without the decorative pediment in the left gable (just over the door to draw attention there) Would you consider using natural cedar for the front pillars and pediment? Cedar is a good exterior wood (pros please correct me if wrong) and looks so great with green siding IMO

The house is adorable. I actually like the yellow, bright as it is. No shutters, and yes, replace the storm door. You live in northern Michigan, you definitely need a storm door. I do prefer one with a lot of glass, but, a requirement for me, is that it also has the pull down storm to reveal a screen. Its pretty nice to be able to open the top a bit, and let fresh air into the house. Something like the one in this link. https://www.lowes.com/pd/LARSON-Tradewinds-Bevel-White-Full-view-Aluminum-Storm-Door-Common-36-in-x-81-in-Actual-35-75-in-x-79-75-in/50375006

LOL okay now that I have read your whole post, I will also add that one of my oldest friends worked for C&J Katz for many years. Who knew I would connect with this post on so many levels? Looking at the pics of their Truro house makes me want to redo my beach house … I love the wacky fixture. And this whole situation. But on to sunrooms. I found it curious that so many of the ”sunrooms” featured in that article are actually porches. For example: I liked most of them, actually, whatever you want to call them, except that this made me throw up a little in my mouth. Why is the coffee table pushed right up against the loveseat? And the curtains…eww. We have a sunroom at our beach house that is long and narrow, sort of like this one — and we have a daybed like this at one end. At the opposite end is a large bookcase, so it is a nice reading spot especially in the winter. Seeing all these pics makes me want to focus on that room this summer and prettify it more.