If the game can tabulate your amount of Zeni based on how many stupid photographs you give to a NPC, and can tabulate your amount of Therion Ichor based on your victories in Einherjar ... then there is NO reason that S-E can't or shouldn't implement a similar system for Voidwatch loot.

"Void Points" (or whatever the hell you'd like to call them) could be awarded for each victory in Voidwatch. The more difficult VWNM's would award larger amounts of "Void Points". "Capping your lights" would award slightly more "Void Points". S-E could implement a daily cap on the number of times one can be awarded "Void Points" for each VWNM (this would prevent groups from spam-killing the really weak VWNM's for Points).

Then, the player exchanges his/her "Void Points" for items.

I do not see why this wouldn't work or shouldn't be implemented.

The current system for Voidwatch loot is absolute crap, and everyone knows it. It's really too bad, too, because (outside of Temporary Items abuse) many of the Voidwatch battles are challenging and can be fun.