Thank you all for these useful ideas. While the jonesing for The Book goes on I have had some looks at Lady Chrystel's and Paul Henry's pages. Both look good. Paul Henry has even a picture of this R'Lyeh tartan there, I think that is a sample of pleating to purple line.

One example I find very tempting is Barb's picture (#6). Might be my choice if continuing on the path of having the professional seamstress but a first time kilt maker making this kilt. Would be nice to have a kiltmaker close. There are not many kiltmakers in Finland, I know none making traditional kilts. Well, not so many using kilts either...

Waistcoat; this picture (#5) of artificer shows a really nice example.
Is it possible to have a waistcoat to be used with kilt and with trousers or do they have to be different?

Day plaid; the idea struck me when ordering tickets to an open-air show in a court-yard of a medieval castle in Finland this summer. The evenings can be chilly and they advice taking something warm with you when attending. But I think this R'Lyeh tartan will become a kilt and I will attain something else to keep me (and the companion) warm. But I am still thinking that having a length of cloth carried as day/shepherd's/shoulder Plaid might be a convenient way to have something warm with you to be used when in need... let's see.