Jaya,
1.? On the buttonhole issue, all of the ideas here seem fine to me, but I'd probably do the fabric or ribbon, mostly because it would be easily reversible.
2.? You've brought up an interesting question with the cardigan.? So if I understand this correctly, you'd be working buttonholes directly into the patterning and body of the sweater, right?? That could look really lovely.? When you knit the facing, you may want to consider putting in a row of purl stitches to facilitate the facing turning to the front.? Knitting that facing from picked up stitches will be so much easier.? Drop down those two needles sizes though (I write this although I realize you probably know a ton about fibery things)
I've only knit two Bohussies, but I recall the front bands are knit bottom up from a few stitches reserved at the bottom and then it's sewed on, right?
I found one Swan with no bands, but she didn't insert buttonholes.? Is this the one you're thinking about??
Mary
Maryu