There are a number of issues I could see with a Saltire flag.
1) It already IS a symbol, we'd just be co-opting it for our use rather than coming up with something new.

2) Flags are fabric, which WILL get dirty, wrinkled, etc.

3)I think it's too big. One of the nice things about the blimp was that members could tote it around. A flag needs to be unfurled to be seen, which might be a little more awkward for members to photograph in settings.

4) As a flag that already represents something, it should be treated with a measure of respect, lest we offend. I don't know if it's appropriate to have it depicted in some of the whimsical situations we all loved to see the blimp pictured in.

I also think, as I said above, that it's too soon to start pondering the replacement of the blimp. Let's give it a bit of time and see if a thought occurs naturally with a member about what (if any) the blimps replacement might be.