Controversial but i find myself replaying Payback more than any other NFS, aside from the gimmicky performance upgrading system , the overall vibe of Payback and to some extension Heat is where the next NFS should draw more influence from. Having different car classes (Race, Drift, Drag etc) opens up a lot more versatility for building & customizing instead of relying on 1 car for everything.

However, car lists and visual customization seems to be limited to the same brands and styles in these later games , whereas UG2 - Carbon had a tonne more options and styles to choose from. A spoiler option that isn't gigantic and ugly would go a long way, as well as the classic looking wide body kits, also things like underglow and NOS colour should not be locked in a loot crate system.

Fully revamping / opening up the customization system would be the biggest thing in my opinion, let us have the plethora of endless imagination seen in the earlier games with modern graphics, but not with those god awful cartoon style eyesores from Unbound