Please don't change Rustic Canyon in any significant way. It's lovely as is.
I rather like the rough tall grass surrounding the bunkers myself. It's good punishment for poor shots.
Also, Rustic isn't really a 6900 yard course. 4 out of the 5 par 5's play slightly uphill and 4 out of the 5 longish par 4's play significantly downhill. 2: 457, 14: 480, 16: 479, 18: 460. 11's a very good slightly uphill 435. 2 plays at least 15 yards shorter, 14 35 yards shorter, 16 maybe 40 and 18 maybe 30 than those distances, not because the tees are placed forwards from the markers, but because of the slope and play style around the greens. No one that's played there before flies the ball to these greens. With a decent drive, it's always an 8 iron or less for these back nine 4's, even in still wind conditions.
7: Great hole as is. Or at least was and will be again soon. I don't see a significant advantage gained anywhere by extending short left.
Some things I'd like to see:
8: I'd change the green to have 3 pin locations instead of 2 without increasing the green size. The back right portion flattened a bit for another pin location and so that balls long with the pin on front right location don't naturally fall back down close to the pin. Now lets see who can control wedge distances to 5 yards instead of 10. The back right would be a tougher birdie.
10: The hells 1/2 acre I don't think will do anything to the good player and will slow the average player down. While this new hazard/waste is where the drainage now naturally flows, it's also where the average golfer puts the second shot 40/50% of the time. I expect this new feature to add to the average round time around 5 minutes. I'd preferred that this feature be closer to the green complex, say finishing 25-30 yards short. Now the second shot for the longish player or the third shot for the average can not be a low bump-run or a mis-hit, but must be reasonably well executed. It also would make a tougher decision for the long player, go / no-go for the green in 2. Maybe the tee could go back a bit too.
14: I think a few extra yards on the championship tee wouldn't hurt, or maybe make a new superchampionship tee. I wouldn't be able to reach the fairway at all from something placed another 20 yards back, so I couldn't play it, but there are lots of people that could use the challenge.
15: I don't care much for this green. There are too many days when if you are above the pin you can not make a 2 putt because the green slope is too severe. I don't see many people attempting to play uphill bump and run sort of shots here. Perhaps a narrow bunker placed just short of the green to catch balls too short might be acceptable.
Other non-course layout changes I'd like:
Remove the back fence from the driving range.
Add more tall vegetation to the course side of the driving range.
Add a chipping green and apron in the practice range on the eastern side.
Remove the wood posts and wire guides, especially the ones up to the 16th tee. It feels a bit penitentiary. I understand these were placed there after the fires to allow time for the vegetation to regrow, but it's all grown back now and isn't necessary any longer.
Perhaps a caddy program? I'd pay for the privilege.
Flatten the practice greens a bit more, too much slope and only half of the actual greens are usable.