Vhista, 

Many shop owners sell things for not only diamonds, but also iron and even gunpowder or other things such as slimeballs. People have their own designated shulker boxes in which they store their things in. It is just convenient when you want to buy or sell something but it's in one of your many shulker boxes that you can easily take out if you had this system instead of going back and forth.
And as Awkwardbowman said, people like to buy in bulk and if they run out of space (which is already taken up by many possible currencies, tools, and food) they may stop shopping altogether if their inventory space has run out or they would have to spend more on eyes. Also I think many people are mature enough to not abuse said system.

Also I forgot to mention that landowicked has installed this system on the side of their shop, many people have benefited from, such as myself - and I sometimes just go all the way there to organise my things - if people would like to take a look.

Places people's shulker boxes so that they can get their stuff out without needing permissions - mainly used for taking out currency like diamonds to pay for things in the shops. It can also be useful for many other purposes like putting the many things people buy in a shulker without the hassle of a messy inventory and can also be helpful when shop owners (mainly peddlers) want to restock many things that exceed their inventory space.

- Why will players enjoy this idea?
I have observed that many people put their currency in their shulker boxes - as well as me and I think it would be a very useful thing to have around - like with ender chests. It also reduces the need to go back and forth from their home to spawn again - reducing wastage of teleportation eyes.

- How does this idea help or enhance the values of WilderCraft? 
This increases the inginuity or want for Wildercraft to help their users in anyway they can. 

- On a scale of 1-10 (1=easy, 10=hard/complex) how complex is this idea?
Not very hard, only needs a couple of redstone pieces, and a simple tutorial can be found online to put it together and perhaps the build team could also help it fit the surrounding area and plan where these stations could go. So I think a 3.