yeah like; to many people the special ability affixing/augmentation system is very intimidating and only manages to take time away from them that they would rather be using to go run another quest. I was just thinking that like, if even only 1-12 weapons and 1-11 units were tradable without requiring premium, it'd open up people a lot more to like; have That One Friend who gladly accepts everybody's garbage items, and refines them into kits for people to at least get their units set up to something serviceable
According to the JP servers. Everything up to 14* rarity is tradable via player shops except armor units which only go to 12* rarity and eggs go to 9* rarity in player shops, but overall go as high as 14* rarity. You cannot trade or scrap items into "kits" as no such thing is in the game. However, if you go to the salvage shop in the shop district. You can trade 10* - 12* weapons / armor units for various items including EX Cubes which you can then trade for fun point tickets at the EX Cube shop. (through updates over time. 10* eggs have been made tradable to the salvage shop)
Just be glad the current trade system isn't like how it used to be back when 10* was the highest rarity and in order to buy from player shops. You had to have premium then go to the salvage shop and exchange certain items for a 10* weapon / unit exchange pass then use the pass at the player shop to trade for the weapon / unit. After several updates later. That was all done away with and is no longer a required thing.