Are you a videogame networking engineer? Because you've just handwaved away one of the most difficult challenges in gaming as if it were "duh that's easy" level simple.

I can link you some GDC videos that talk about how hard this problem is if you want

ETA: Also you've only addressed memory modification attacks. This does not address external aimbots that read memory to determine enemy player position and then send legitimate-but-automated inputs to aim and shoot. How do you stop cheaters from doing this when they can see exactly how data is structured in memory, how values are obfuscated, etc?