Seriously, VW loot system..come on.

[Prothscar]

Having the monsters scale their difficulty, but also scale drop rates, based on the number of players engaging them, say from 6 to 18, would be a reasonable strategy to make Voidwatch more accessible while still making it profitable for a larger group to take part in the event. Obviously the drop rates would also have to be reconsidered as making them even lower than they are now for smaller groups would be preposterous, perhaps have a smaller group of 6~10 people have the drop rate that exists now while a larger group would benefit from enhanced drop rates. A larger group would also benefit from having more reliable procs.

This would serve to, again, make Voidwatch more accessible while still making it rewarding for larger groups, and it would also retain the difficulty of some of the T6 fights (which I personally enjoy).

I would also propose the addition of a token system, similar in fashion to the Trophy system added in Heroes of Abyssea. Tokens would be NM specific and could be traded in to an NPC for the items that the NM drops. Tokens per NM would also be based on group size to maintain the larger groups still being worthwhile. Only the higher tier NMs of their designated chapter and branch would drop these tokens.

Let's say...

Hahava - Intolerable Token
30 tokens - Ganesha's Mask
50 tokens - Ganesha's Mala
80 tokens - Mextli Harness

Voidwrought - Impenetrable Token
30 tokens - Strendu Ring
50 tokens - Strendu Mantle
80 tokens - Fazheluo Radiant Mail

Pil - Varna Token
30 tokens - Aliyat Chakram
50 tokens - Dilaram's Sollerets
80 tokens - Toci's harness

Kaggen - Mantoptera Token
30 tokens - Mantis Eye
50 tokens - Phasmida belt
80 tokens - Mekira Meikogai

Qilin - Zodiac Token
30 tokens - Houyi's Gorget
50 tokens - Fajin Boots
50 tokens - Lux Pugio
100 tokens - Coruscanti

Etc.

Could also add an option on the NPC that allows you to trade certain tokens for certain Magian Trial items so that, after someone already has the drops that they desire from each NM, they still have a reason to repeat the fights.

For example:
5 Akvan, Kaggen, Pil, Qilin, Aello, or Uptala tokens - 1 Riftsand
10 Akvan, Kaggen, Pil, Qilin, Aello, or Uptala tokens - 1 Heavy Metal Plate
80 Akvan, Kaggen, Pil, Qilin, Aello, or Uptala tokens - 1 Heavy Metal Pouch

10 Gaunab, Ocythoe, Kalasutrax, Ig-Alima, or Botulus Rex tokens - 1 Heavy Metal Plate
50 Gaunab, Ocythoe, Kalasutrax, Ig-Alima, or Botulus Rex tokens - 1 Riftdross
50 Gaunab, Ocythoe, Kalasutrax, Ig-Alima, or Botulus Rex tokens - 1 Riftcinder

1 token per fight for a group of 6~11
2 tokens per fight for a group of 12~17
3 tokens per fight for a group of 18

This would still mean that content is repeated several times, but it will also mean that you are eventually guaranteed the drop that you're after. This sort of system would not shorten the lifespan of this content for most people, quelling any concerns that the Developement Team may have toward that topic, however it would allow peace of mind in that after a certain number of successful fights, you are guaranteed to be rewarded.