Let’s say.
I plan my game to have 2 different reward code systems:
Global Codes
Basically the common reward code system, where devs post codes on social media that then can be redeemed for rewards in the game, like [XQW2M-KK41D-0PMS3]
Item Distribution Codes
That’s the new way that I am talking about, where an user can convert some of their tradeable items into a code, that then can be used by a person to redeem attached items. Maybe even I could make a system which allows users to include a message with the items.
Non-tradeable items would pop up an error that they cannot be converted into codes.
Codes would be one-use-only.
But is the second way really worth? The concept seems like 2 months to code, will it be worth?
Firstly it doesn’t have to be 2 months to code if you can hook it up to some external servers that manage the code assignment and contents.
Secondly, I don’t think this method would be used a lot. A lot of the player base on Roblox are young children who would much rather smash in a code they found on Twitter than set up their own code and distribute it to one person. Why not create a trading system where players can send their items to a player?
Hope this helps,
-Tom 
Trading systems can be used to scam people. Plus, with codes, you could do a giveaway really easily.
Surely it would be a lot easier to scam someone with a code than a trading system because people don’t see what’s inside the code.
Let’s think about the realities of giveaways, giveaways would be cool if it was on social media (ie the global code system). I don’t see any reason for a general player to do a giveaway with their items.