Random ship / group spawn

[ADM Mako]

I've got a question and haven't been successful in searching for a solution here, and the manual doesn't really cover this well enough.

I have a scenario I'm working on where I want several groups of ships, subs, and biologics to randomly spawn... but in a logical "if/then"manner.

For example, I have a single attack boat as GP1 (25% POI), an attack sub and a missile boat as GP2 (50% POI), and a diesel boat as GP3 (75% POI).

What I want to happen is that only one of the groups actually spawns, but which one actually does is randomized kinda like this :

IF GP1 exist GOTO END
ELSE
IF GP2 exist GOTO END
Else
Spawn GP3
END

(I hope that makes sense)

Is this possible within the scope of the script editor? Or is there another method to accomplish this?