-> Please bear with me for the long reply...
In my opinion, there are tracks and track variations that PD can easily do in a short time. I know I saw another forum topic on this, but I'd like to have a say in what other courses could come back easily:
1. Suzuka West (why is there an east version, but not west?)
^ I think of the East Course is being way overused, from the
F355 Challenge to
Forza 4. I see this track almost at every game/simulator!
-> I treat the west couse as the Japanese Dunsfold Air Field (aka.
Top Gear UK Test Track) when I was playing
GTPSP testing cars. And of course, I don't forget the West Course when the Manly-Man Senna had a go with the epic NA1 NSX Type-R:
^ Yup, as his jacket says...he's DA BAWWSS!!!
2.
Tsukuba Short (it even appears in Tsukuba itself!)
^ It was featured in some sims (ie.
Forza series). Why not in GT!? It would be
perfect for even more drifters! 
-Tsukuba Short-
3. Tsukuba Wet - Weather Changes (if they have weather effects, how come they didn't bring back the rainy version from GT4?)
^ It was a blast back in GT4. In fact this was the first Wet Course I've enjoyed ever since! 👍
4. SSR5 Wet - Weather Changes (for the same reason as #3, also that this was also a course in GT3. Also, how come SSR7 gets to rain, but SSR5 doesn't?)
5. Clubman Stage R5 - Weather Changes
^ I believe PD focused too much on the
incomplete SSR7.
6.
Motorsports Land (if they can make Kart Space, they can make this easily since there are now Go-Karting races).
^ Motorsports Land IS THE PERFECT KART TRACK! Period.
^ Why oh why PD can't see thru GT2!!
^ I remember '90s and the much boring '00s version.
I totally miss the '90s version...
^ Same as #7 above...
-Mid-Field Raceway 'The 1st'-
^ Even thou its one of my least favorite tracks, it deserves a comeback.
^ There are two of them now!
11.
Motorland since it should not take too much effort to redesign these tracks, as they are original tracks and not as overly detailed as Spa and Kart Space.
^ I already posted on the 1st page that Driving Park: Motorland is pending to return in GT5
-Driving Park: Motorland-
12. Possibly Piazza del Campo, since PD already created the track (it even appeared in
demos and as a Photo Mode Travel Location!). Just don't worry about those flags and make it a course anyways!
^ Obviously, just like what they did on the JLOC-Nomad Diablo on GT3. Piazza won't show up until GT7...
13. Fuji Speedway '80s
14. Fuji Speedway '90s.
^ Don't forget the '70s version:
And more easy ones...
15. Complex String (this may take a little longer to recreate than the others I mentioned, since the track is incredibly long, complex (as the title states) and full of various elevations, but again, it's an original track. Try porting it from GT3, for starters, and fix details here and there. Also, don't limit it to time trials and free runs; make it a single/online/ENDURANCE race!)
^ I used to remember back then that
CP was one of the most unliked tracks in GT3.
^ But now, the track gained its cult following and it resulted back to one of the most highly demanded tracks in GTP after GT4! On which now brought to its
Legendary Status.
16-17. The Monza 1955 variation, the one with the oval (even Naruto149 found
this out!) Oh, and there's also
Monza Jr.
^ It would be possible as PD did with the Fuji '80s track before. All PD has to do is to aquire as many data as possible from Monza Track officials.
18. In GT5's version of SSR5, it
appears that, in the first tunnel, they've added a pathway that apparently leads to SSR7. Here sparks a new question: where does this passage actually lead to in SSR7? Could it create a whole new combined track?)
^
That pathway to SSR7 leads to a different section of the highway outside the intended section of the highway. On SSR7 in GT5, there were no notable exit/entry on ramps on th whole course.
19. Super Speedway, GT2/3 version, not Twin Ring Motegi's. Very easy to remake.
^ As I pointed out on my 1st post, the Super Speedway '00 in GT3 is pending for return. The GT2 version/'90s has a different scenery and pitstop layout. The Motegi is just plain boring.
-'90s aka. GT2 Version-
-'00s aka, GT3 Version- (pending to return in GT5)
-Motegi Version-
I'm with you, Vanishing Boy; it bothers me on why PD would exclude tracks that should have been there in the first place, especially numbers 1-4. If they can easily make Spa and Kart Space, then aren't these tracks I mentioned easier to make?
^ In my opinion, GT5 is a prime example of being losing their focus...im mean PD could bring back all these tracks with minimal effort instead of creating a whole new Original Track.
