Brake upgrades are interesting. I've done this on a few race-focused cars, and changed my truck to get better braking with the camper, so I know what you are talking about.
Slots/drilling are cool looking, and intended to help with pushing water out faster, so the initial "bite" happens more predictably. They also weaken the rotor.
Rotor thickness (new, vs turned) is critical to dumping heat and preventing warp. SOME cars have lousy OEM rotors that warp fast and swapping for after market heavy cast iron rotors can make an improvement there. The Frontier doesn't seem to have that issue.
Pad material determines initial bite vs high heat tolerance.
If you can tolerate replacing rotors more often, get a more aggressive pad.
Stainless brake lines also help with "feel" and brake control when you are pushing it to 9/10 of yours or the vehicles ability.
When are you noticing the lack of "enough" brake? My brakes tend to last a looong time because I use the transmission to do a lot of braking.
Beyond that, some trucks allow for swaps from similar and bigger rigs. That does not seem to be the case with the Frontier though. The only reliable option out there is very expensive
That's my $0.02 on brakes.