So most would agree that straight up trading would be bad for destiny. Duping would soon follow. There may be a solution that does not break the game.
Imagine you gather your raid team, knowing that four of the six guardians are greenhorns. Two of you are seasoned veterans of hundreds of raids and have amassed as much of a stockpile as possible between the two. One of the vets looks at one of the rookies and tosses him a SUROS Regime, "give it back when we are done kid." Soon the four rookies are armed and armored in gear fitting the task at hand, and the raid goes well. After the dust settles, rookies no more, the four first time finishers hand back the borrowed gear, thanking the grizzled veterans.
This is the answer! Not trading, but loaning!!!
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There is a problem with your concept. Say if someone had to G-Horns and lent it to another friend. Or what if everyone in the raid was able to have G-Horn because some people have more then 1? It would be very easy, and would diminish finding certain items to keep. They should just introduce a trade system... Exotic for Exotix Legendary for Legendary Etc... And to prevent crazy trading, it would cost a strange coin or 2, maybe even glimmer. This will prevent people trading 24/7