Firstly, I would like to point out that I think these game modes should ONLY BE USED IN WARS. It partly defeats the point of the game but should be used in wars as it would be beneficial to them.
Here are my ideas:
Racing only game mode:
I know some people have been thinking about this before, I personally think it would be good for COMPETITIVE GAMEPLAY i.e. wars, tournaments, etc. In this mode cars can not hit eachother; basically, the cars act like they are holograms, as they can overlap eachother and come into contact but no damage is done (no clip mode). This would mean no launching or lagging of players. You could argue that part of the skill of racing on NFMM is to avoid being lagged and taking the right chance to overtake your opponent. However, I believe this mode would be beneficial in some scenarios as cars such as Formula 7, when racing with a Radical One, are subject to either being launched into oblivion and put out of contention to win the race or one hit KO'd and wasted. This puts such cars at a disadvantage as users have to brake and try to avoid being hit by Radical Ones knowing that if they were, their race would be over. It would also mean there would be no intentional dirty racing in wars.
Wasting only game mode:
Highly self explanatory, basically a game with no checkpoints meaning all players must waste.
No (insert car name here) game:
In this mode, you can select specific cars that can not be used. If you are a person that finds MASHEENs insufferable, yet you still want to play with Class A cars, you could merely select no MASHEENs.
I know my explanations aren't very clear or articulate, but I hope you understand each of the modes. Please note that obviously if the modes were put into the game normal modes where wasting and racing is available would remain the norm.