The problem with stretching a low profile tyre is that the offset needs to be spot on and the guard needs to sit either right on top or over the tyre a little to pull off the look IMO, otherwise it just looks a little strange. I know what you're saying about having a smaller tyre overall to bring the car a bit closer to the ground though. For instance here is a pic of my RX2 with one of my 9in BBS on the rear I was trying for sizing(let me know if you want the pic out of your thread), they have a 215/40 on them and work well on my wagon(being lower), but poke a little too much on the 2 for me, plus I'd want it at least 1/2-1in lower if I was to run this sizing. The other wheel I'm thinking don't have as low an offset, but are still a 9in, I'd probably go a 225/40 on them with quite a bit less poke, this is why I'd want coilovers, to wind it down another inch or so.
What width were you thinking front and rear when you rebuild yours?
Keen to see how your seats turn out....I'm planning on having mine trimmed in as close to the wagon's original colour/pattern as possible, so they look like they might have been a factory optioned Recaro....either that or if I can't find the material I'd go something custom, but period custom, on both the front and rears then.