How vital is the short soaker tub to you? You said there is a pool already on the property.
I've been looking at tiny builds for a few years and also considering some of those ideas for our basement upgrade.
Being able to age in place is something I've been putting at a high priority so am trying to plan in accessibility.
For a small bath, making the whole room a "wet" room seems to give the best space, access and usefulness value. A folding, wall mounted seat and a flexible shower head, with no closed stall, would make it very accessible, even with the small size. Easy to clean too!
For the kitchenette, my uncle did a bunkie a few years ago and the one he did was to put in a short bit of countertop that was just wide and high enough to go over the top of a bar fridge. Total length is a bit over double the fridge space and the rest is closed shelving. Open shelves above and there is lots of room a kettle, some canisters and any room temp foods on the countertop.
The same bunkie uses sliding glass doors as both the doors and the full length windows. Shows the best views and you don't lose another wall to a door.
Last thing I can think of is if you can cheat on the porch issue by using a sun sail? It's not permanent, so it shouldn't count but could give you almost the same benefit.
