I have seuggested to the Devs about adding Mondello Park (Irish track, its in GT Legends) before. I know the owners and i have been told by them there would be no problem in adding this track for free (maybe in exchange for some free licences for Mondello to use). I even offered to go and take all the pictures and video needed. But the Devs didn't take up my offer.
I know it's no nurburgring or leguna but it is a pretty good track and has some nice corner combo's and has some great overtaking places.