You both have a good point about the Frag market and hw this might not benefit those who actually compose.
And unfortunately my argument to support one, is at the cost of the other
I would say to the people who do compose that while they still only get 3 chests the availability of MORE frag chests from guild mates ... but this would still result in the frag market taking a serious hit
From what you have said I would add the following:
1) This can apply to all global quests, not just frag ones
2) The amount of kills needed to get to these tiers is flexible... I trust the cows to determine what would be fair
I will admit this idea has more rough edges than a Redneck in Paris. An idea in motion more than anything else