BAD IDEA.
If you're organising the collection he's not liable for anything that happens to it, and a guitar only in a gig bag will almost definately get wrecked.
+1
VERY Bad Idea.
And to be fair, I would have some sympathy for the courier in that situation.... if the item's not packed in what anyone would consider a
reasonably secure manner, how can they be expected to "baby" it so it doesn't get damaged?
Have you already bought and paid for this guitar?