I like the idea of 'vehicle stealth', though the terrible vehicle made it frustrating. I played in 3rd person mostly as the car bouncing around so much off road was a bit sickening. Some quick thoughts;
- Perhaps lean more heavily into the stealth aspect. Have buildings (barns, warehouses, petrol stations) scattered around for the player to hide under while enemy flies over head. If an alerted enemy spots player enter hiding spot, you could have them destroy the roof/blow up the entire thing. Could also have engine noise being part of what alerts the enemy, so at times player may want to turn it off while hiding, or while rolling down slope.
- Once an enemy is chasing me, I was rarely able to escape it while offroad.
- The cars suspension was too 'bouncy', combined with the low poly terrain made getting around off road a bit unpredictable. Really feel the terrain should be smoother.
- Terrain should probably be flatter over all. Be a bit more forgiving for traversal (car can barely make it up the steeper slopes) and allow player to see keys in distance.
- Highways/roads were too narrow, it's easy to hit side and fall off. You also can't even turn around on some of them. I'd suggest doubling their width, but including hazards like abandoned cars and broken sections.
- HUD for third person.
- There wasn't much point to having the headlights one given how bright things are. Perhaps make things much darker and include some hazards you'll drive into with out them (trees, rocks etc). Could explain the darkness as an eclipse or giant 'sky friend' blocking light.
- Should be an audio que for enemy becoming alert, as well as, going back to roam state
- Working rear view mirror would be a nice touch and would make being chased more intense.
- Be nice to have radio to listen to, could have player provide URL for internet stations. You could also tie this to gameplay with having enemies broadcast things over it, like their alert sound
- Cosmetic damage wasn't so obvious in first person, maybe have some more exaggerated things like losing doors.
- You could make key count UI indicator diegetic like the damage indicator. Keys could be shown sitting on dashboard for example.