How would you like to earn currency?
Events, like how @Oreo said. Amount from opening crates, doing compounds, ect. Getting robot kill could drop some but make it a small amount to avoid people abusing it to a lot of stuff by just camping airport. You should get some for player kills, and depending on your're killstreak get a bonus amount if say 1 kill you get 10 and on a 5 killstreak you get 50, and then if you kill someone that has a killstreak you should half the amount he was on, so if a player is on 5 killstreak and 50 coins if I was to kill him I'd get 25 coins. Kinda like the bounty system on NewZ. Also you could add it as a lootable item, that would make looting more rewarding kinda like h0w on Stattered Skies you could find legendary guns parts which if you found 10 you could make a legendary gun box for a random gun.
What items would you like to see from traders?
Meds 100%, maybe not like military meds, or put those on a timer. low tier weapons, ammo, and crafting materials, and if you take out /outfit you could add those too. Or make some new ones and add those.
What is your vision for how traders would work?
Mainly, to help out new players. The reason most people leave is because they get on for an hour, loot around and find some guns only to lose their GI and not feel like looting again too actually learn how to play the game correctly.
Where would traders be located? What are your thoughts on limited time traders that have a shifting inventory?
Each safezone, I'm also a fan of one somewhere around the map. This could be a good time to actually impliment and nonSZ GI, have it be a small outpost that looks all war torn, and worn down. And have the trader be behind some bars or bulletproof class making it look like a sorta Stalker trader vibe.
I also +1 what @Kuush said, It'd give people insensitive to maybe kinda not SZ pvp