[Esther]

Simpler suggestion:

Trading items is completely unrestricted by key or IP address. Instead, it is restricted by the following, single, simple rule.

In order to receive an item in a trade or purchase from a player-run auto-shopkeeper, you must have reached a character level of 6 times the item's rarity stars. As the lowest possible rarity an item can have is 1 star, characters 5th level and below cannot receive items from other players. At 6th level, a character can receive 1-star items. At 12th-level, 2-stars, increasing all the way up until finally at 60th level, one is allowed to receive 10-stars in trade.

Any item purchased from an NPC vendor (such as Air or Zeo) or dropped as loot from a monster, core, chest, gathering node, farmed crop, deconstruction/crafting result, quest, laplaceNET request or laplaceNET present tab are unaffected by this rule..

This does multiple things:
1.) It prevents the real problem: characters receiving things mechanically more powerful than they should probably have at a given point in the game, just because they have a main or a friend with a main.

2.) It prevents IC from truly being broken, as the rule is both simple enough to understand and tied to a character's IC ability, that a character wishing to give another a gift during roleplay can easily know whether to open a trade, or say something along the lines of 'Hey, I have something I want to give you when you get a little stronger, so keep at it.'

3.) It is completely divorced from murai cost. An IC service to deal with an inconvenient, poorly-worded OOC rule is the antithesis of roleplay.

4.) It opens up the possibility for truly legendary, incredibly difficult to find 11-star items in the future, that can never be traded away from the character that found them.