Personally...I would sell the bike for $3000 - $3500, depending on the condition, and put $1000 - $1500 with it and look for a 2016.
I would be afraid to put $1000 into the project and it still comes out looking like shit. I'm no fabricator, nor do I like tinkering on that level. Plus the 2016+ are supposed to be the cream of the crop by 125 standards. Also everything points to the 2019 being the next generation although we won't know for a few more months. If it were me, I'd sell that '15, put that money plus what you would spend on the project on a left over 2018 since the 2019 will likely be heavily updated, or just go ahead and buy a 2019. I bet you'll be able to find a brand new 2018 for $6500 OTD or less come May or June.
When I was younger I really cared about having the newest bike on the block. These days I just want to have a bike that is in good shape and performs well. I don't think its worth it to go barrel scraping just to have the next newest body style...you could end up buying a money pit and you'll wish you never got rid of the old bike. But YOLO! Lol...good luck.