This is a shame for sure. Looking at what you have to work with, it is going to be hard to live with a repair of any kind. You could do a temporary repair, hide it with a stock wrap, and search for a good replacement buttstock. I think the repair and cover will cost a good portion of a replacement buttstock, so, you might just want to start the search now. Check all the usual suspects for price and availability, and watch ebay, as they pop up there all the time. Best of luck on the stock.