I have heard from a few people now.
The responses have basically come back with :
This isn’t weld, it’s joint filler / seam sealer
Despite looking like metal, it isn’t metal, it’s a type of mastic and can be dug-out with a screwdriver. it also goes over what are apparently plastic caps, so therefore can’t be welded.
One useful chap on Saabscene has had a look at all 4 of his 9000s, and they all show similar cracks, so it isn’t due to the strut brace or being used on a track.
The filler can age, and even after 10 years it can still be changing, hence cracks appear.
So basically, no worries on that front 🙂
If I am keeping the car garaged, I don’t need to worry too much about water ingress, and people seem to consider these pretty minor cracks.
That’s one less job for me to do. I am also tempted to leave the front wings as they are (i.e. looking very good!). If the car stays dry in the garage, and the dots of raised paintwork don’t change, then I’ll delay any expensive work. Also, should I fit new wings, surely I would be guaranteed to bend the car at the next trackday…