Well, sign shops yes and no.
Yes, they are there and you click on them. duh.
No, There are plugins with auto protection, you put a chest and a sign, no one can break it, creepers don't work here to avoid the usual chaos, and you can't also blow it up, but you can blow up everything around it. And they also need knowledge of what to write the sign.
(It could be worked around with worldguard, area, build yes, tnt no,)
As so, I don't want the desert covered with chests or some other place around spawn, you have to teleport there, you have to go there and refill it, bla bla bla
Exchange market is a way where you can trade on your cell phone, while sitting in the toilet kinda a thing, like twitter
sooooo... sorry, no chest shops and no way for redundant plugins.