Appreciate all the feedback. Here's floorplan, which I think I posted before and got great help with from the architect POV too. As we've gotten deeper in our process with these things, I think our appetite for a larger potential scope of work has changed too.
In the end, what we want down there:
1. An office/guest room
2. A bathroom
3. Laundry/linens
4. Space for exercise room (weights + 1 cardio machine)
5. Storage
6. Family/TV room
7. Make the stairs safer and real stairs (will impact all floors of house)
Potentially, depending on other parts of house:
A. Mudroom stuff
Because we started by approaching naively, we were like:
- Workshop --> bedroom
- Existing family room + bathroom
- Laundry area gets some polishing up
- back/other area gets a floor, basically, and turned into exercise space
- stairs get slight adjustment/expansion roughly in place
But generally what we're realizing is that the bathroom forcing the hallway to be against the wall, and other things related to thinking about the existing workroom/family room as "locked in to place" have made us really limited in our thinking about potential floorplans.
So if it's actually not that much more expensive to move things around, why not? The finished living space sure, that's easy that's just moving walls around (roughly), but the bathroom has pipes and stuff?
All thoughts appreciated! We have been interviewing architects about upstairs and downstairs, but haven't made any decisions about really anything yet.