Hey Op,
I'll take pity on you, seems no one is interested. I have 5000 hours flying on MPA (mostly, but not all Nimrod)
Assuming your spec id for long range maritime patrol, also known as blue water ASW.
Range/Endurance - The ability to transit long distances and loiter on patrol.
Speed - to get on patrol relatively/reasonably quickly.
Capacity 1 - to carry weapons, sonobuoys and other ordnance
Capacity 2 - to carry a largish crew
Capacity 3 - to carry a full sensor fit (radar, acoustics and other stuff)
Capacity 4 - to carry a load of communications equipment (LF, HF, V/UHF, Data Link, Satcomm etc)
Aircraft Systems - needs to have electrical capacity to drive all this kit and the cooling capacity to stop it overheating. Needs system redundancy to keep the thing operating at a consistent level. Needs the ability in terms of engines, handling and avionics to operate at low level over the sea for very long periods.
that should get you started.
Other aircraft types, smaller a/c or helos as mentioned can do shorter range stuff, but at this moment in time only fixed wing large aircraft can do long range maritime patrol.
Technology might change this one day, but it aint' here yet or even close.
PS and yeah, to keep everyone happy..it needs a galley.