Agreed. explosives are underwhelming. FF is very important, but unfortunately its gonna create a lot of opportunity for griefing on FT
Berz Is strong now because he is beefy. Yes, more stealth is going to be required, but stealth kills are HIGHLY limited, and that is intentional. Berzerker should have to stealth to some extent just like every other predator. That is how predators are. However when the shit hits the fan, the berz should be beefy enough to get in there and put those melee weapons to use. Of course with my changes, all predators would be a lot more squishy, meaning that berz will be the best at making use of the melee tools.
Stealth kills, being extremely slow, but extremely strong are designed to strike fear back into the fire team. Because of the extreme limit to one or two maximum per match, I do not think they will be overpowered. The animation should be at least 10 seconds, and then on top of that, the damage resist super buff afterwards, while 30 seconds might be a bit much, should be long enough to give the predator a chance to punish any fireteam members that think they are hot shit.
Fireteam pistols being a default would be interesting, and I do like that idea, but unlike pred, who only has one variant of plasma caster/wrist blades, fireteam has multiple pistols. That being said I think that the fact that the fireteam has back up weapons aside from pistols, in either the current way, or the way you describe, is perfectly reasonable. These are special forces after all.
Pred needs more gear in general, Not just different kinds of traps, but recon drones, like the falconer in predators. Other really neat stuff like that would be awesome. As for a new class, I dont think that they need any new predator classes. The classes are meant to fit playstyles, and nothing more. the equipment he brings is essentially the class.