I am not an airline pilot or ground crew member, but am an aerospace engineer of some 35 years standing, having worked on mainly military stuff.
Forgive me if someone else has previously raised this point, but I think not. It seems to me that, having read all the preceding posts and watched intently the video
( - particularly at 8.45mins in!) there may be a 'bum trick' been missed by other posters concerning the cowl latching on the V2500.
If this video illustrates the current latching system, and I'll be the first to admit that it's now some 3 years old, so may not, it appears nevertheless that each cowl latch may be able to be pushed home/flush WITHOUT THE HOOK OF THE LATCH ENGAGED on its corresponding pin/toggle and the LATCH HELD FLUSH by it's trigger/button! The cowls seem to fall closed or near to closed in this situation.
I cannot therefore see any way in which, given this scenario, :-
A) the latches could be easily observed to be unlatched, on a walk-round or by ground crew observation or the like
B) any painting of the latches in fluorescent colours or likewise would aid the identification of an unlatched latch
C) the cowls could be easily seen to be gaping/unlatched with the aircraft at rest.
Having looked at the latch design (from H******l, I assume) it seems not beyond the wit of man to engineer a latch that CANNOT be closed unless it is fully hooked onto its mating pin/toggle, such that unlatched latches would definitely hang down from the nacelle. Paint 'em fluorescent then, if you like, and they would almost definitely be noticed!