To weigh in on this:
From what I have read, the OP is offering a solution that:
1. Tries to restrict trading to the point of "well you didn't earned it from playing, so you can't trade it again"
2. Focuses on alt accounts made for reselling items they got, one way or another
3. It assumes that it's in DE's best interests to limit their playerbase's freedoms to do anything they want with the items they have in their possession, regardless of where they got it
4. It assumes that players who are "gifted items" are indebted to the giver and as such, should act regarding these items on the basis of such
I have problems with how the topic is approached (point 2) and discussed (from further replies of the OP). By only focusing on only one segment of the playerbase, any suggestions to restrict it is just wishing ill on the other segments who have other motives that might be more legitimate that what is being discussed.
If a lower MR player (which I won't assume if alt or not, it's not our business to know) gets an item, it's theirs. They can do whatever they want with it, charity be damned. Although I myself would personally respect such actions (was gifted a primed set before, and have built-rushed the same items out of respect) and want those I give to use it well, I can't assume that everyone would behave in the same way. All that we could do is to hope that they benefit from it, in which, if selling it for plat is beneficial, then so be it.
Here's a different perspective, instead of focusing on "stopping alt accounts", why not just promote "legitimate trading with all accounts, with no assumptions if main or not"?
Here's an alternative solution:
1. Instead of outright restricting trades of a particular item once traded, put them on a "temporary timer", minimum of a week, maximum of a month (should depend on the type of item, and the MR of the receiving account). This would not immediately deter unwanted trade behavior, but it ensures that such actors are barred from quickly performing their plans at the soonest.
2. To address "sharing items between friends", why not implement a "clan stash box" that allows clanmates (who are usually friends) to leave items for specific members so that they could share items without waiting for each to be both online. To prevent abuse, have it so that shared items cannot be put up for trades by anyone except the primary owner of the item.
3. Any plat earned from trading will be put into a "temporary timer" as well (should be based on the MR of both accounts, as well as the amount earned), restricting usage to the market until such time expires. This also doesn't deter unwanted behavior, but can delay such.
4. Implement a "premium trading license" probably 500 plat for a duration of 30 days, where the restrictions of points 1 and 3 are severely reduced, a "verified check" is shown on the player name at the trading screen, and taxes are slightly reduced for both parties. This legitimizes "flippers", but also allows DE to focus their efforts in monitoring trading behavior on those who aren't.