soloing is pretty much impossible in chopper.
No it isn't, people still do it, I've seen an attack chopper being solo'ed in a public game a lot of times, people would just randomly grab it when it spawned and went flying around trying to strafe enemies with Hydras and got shot down, I even had a WZ10 on Qinling in 0.75 trying to destroy me in a Linebacker by flying low and firing Hydras at me.
Of course it isn't effective, but that doesn't mean it doesn't happen.
If anything, the weapon usage delay could at least be there to simulate the fact that in RL pilots don't just jump in and start firing their weapons.
And I like the 4 second delay on .50s tbh, I know that sometimes you can be really devastating parking a jeep somewhere and hop onto the mg and rip apart everything, but people that drive around alone in a jeep and immediately switch seats when they see an enemy really piss me off.