One problem with humans it seems is how weak they are compared to Pokemon... so many human players use NPCs to boost them up, and while tanks, jets, and such are great they don't make for the greatest of battles...
Basically give humans battle armor (Thick armor, good weapons (some melee weapons like claws and swords), and some the ability to *jump* for short distances with like a rocket pack). Basically something for PC humans to use to bridge the power gap. (The armor is thick enough to outlast several pokemon attacks)
Also start delving into human enhancements (replacing your arm with a mechanical arm, eyes with mechanical eyes, etc), and make them more common. Of coarse there could always be a stigma with the devices that people who over enhance themselves lose their humanity.
Tanks and such are find for the large battles I think but for smaller player skirmishes they just seem too big/powerful to make for a decent battle. Also not limiting humans too much would be good (the permission thing needs to be changed IMHO to where human players can get new weapons and such without having to request them... I understand some limits but not simple infantry weapons).