I have found a solution to your problem, although not specifically my solution. Here it is.
Multiverse-InventoriesMinecraft Version Not Confirmed and Per World InventoriesMinecraft Version Confirmed 1.8 1.9 1.10 1.11 .
The idea behind the two is that, if you have separate 'worlds'/realms for different activities such as mining and or marketing so and so, you will be able to maintain players' inventories between them all. So a Trading Inv. for a Trading World< Example and a Mining Inv. for the Mining World< Example and so-on...
They're both relatively easy to use and branches off-of Bukkit / Spigot and have attached instructions.
(Keep in mind that 'Multiverse-Inventories' is no longer maintained and wil not receive updates, the creators have included a note in their post)
The APIs are a peach too! That is... if you're into programming like me :happy_face: .
You'll find that one of them, fits your needs.
Good Luck.
Note: I could not find anything, from my time doing searches, about 1.7.10 mods/plugins that helped with this, sorry. But if you feel like upgrading to a higher Minecraft Version, you'll find that this became a whole lot more useful. :smiley_face: