Unless i missed it, did you try calling another dealer to verify that there is no other stock in your state? And what they have to say about timelines to get another one?
Personally i wouldn't take it. Maybe that's just me but if i paid for new i expect new. I do like what Cees Klumper said above to make sure it's documented somewhere in case something does show up later on If you do take it, and don't let them off that easy.
If only there were another dealer... We're not a big state, so literally one company is the only authorized BMW motorcycle dealer (or at least that's what the BMW website tells me). The only motorcycle brands that they don't own are Indian and Suzuki. I've reached out to a couple of BMW dealers in SoCal and Seattle to see if I could buy one from them and have it shipped to me. We'll see if they get back to me, or if they think I'm just plain nuts and ignore the request.
As far as timelines go, since there are no other ones in inventory, they have to wait for the factory in India to "post" unfinished 310's, then pull them down and select options like colors, additional equipment, etc. Then the bikes finish production, get shipped back and forth across the Pacific, go through customs, dock workers etc., and then show up at the dealership. There aren't any bikes in this production pipeline, so timelines are Q1-Q2 of 2019 for another bike.
Yeah, I don't plan on letting them off easy. I'm certainly planning on making them fix every little scratch. And if we can't come to a mutual agreement on, at the very least some sort of warranty for the possibility of hidden damage that BMW won't cover, I'm planning on making this situation a little more visible to management in, and then people outside their dealership. Given that their Yelp page is sitting at 1.5 stars, I'm not sure another review would result in the desired outcome. On the plus side, at least someone responds to the negative reviews they get.