I think PD needs less of a challenge, tbh. Time spent making new tracks could have been used for making more premium cars. OR.... crazy as this sounds, actually include the freakin' Trans Am for a change (in the 4th Gen it could be just a palette swap for the camaro, wtf?! But no, shafted again!), or the production Solstice Coupe and Roadster.
However, that aside.... I do appreciate new tracks. But as someone pointed out, they can shovel some old tracks, so why not others? It's not as if in cluding all GT4 tracks is "remaking GT4 over again". AND... re-adding some that have been lost would be just like adding new content anyway (Red Rock, SSR11, and Grindelwald for ex.). What makes certain GT1 tracks more special than others? Yeah, Grand Valley is a classic, but so were Midfield and Apricot Hill - and SSR11, and El Capitan, and.... on and on, really.
It would be nice if they could be download content, but would have been nicER if they could have just tossed them in as well, just as they were, and maybe either state that no further development was planned, they were just added so people could use them, OR, work on them whenever they get around to it and release updates, or even as part of GT6 maybe.