I'm the same on this, I'd really love to have the extra tracks in as it would make it an AWESOME game, with 26/27 total tracks. I loved 2013 with their extra tracks DLC. I totally hear Mather about the issue of development time as well though; however if there is any way they could get even some of the extra tracks on, they should go for it.
For example, Imola was already on 2013 DLC, so they already have a copy of it to start with.
Nurburgring was also on 2013/2011, Turkey was on 2011, so they have a broad outline to begin with.
Bahrain outer is also really short and simple.
Portimao and Mugello would have to be done from scratch, or copied over from a different developer, which I get is difficult.
I hear that the main issue is coding AI. If this is the case, then why not make them ONLY available for online multiplayer, so only real people can race the tracks, and there is no ability to add AI? Not perfect, but if it allows them to do it in time, then why not?
Come on Codies lol! If there's any way to do it, even for just a couple of them and without AI, then please do it. Would be an awesome addition.