I Really Advise These Plugins As They Are So Fun and Amazing But If You Need More Info You Can Find It Here! Move Craft: This Plugin Enables you to make masses of creations like planes boats tanks and etc. And make it move! and this isn't like a sore eye thing you actually need a amount of stuff to make a bout like you need a sail and a wood base then for a plane you need stone/iron/wool and with coal blocks you can make real torpedoes! That Can Set Of Wars Between Towns And Action! also you can have Cannons On Tanks! This Plugin Also Makes A Fast Fun Way To Travel Even If You Are Tired You Can Just click a sign and move forever till you wanna stop! And Its Cool Because cars and tanks can make up hills! if needing more info:Minecraft : Movecraft Tutorial - YouTube SlimeFun: I Loved This Plugin On My Last Economy server but it went out :~:! But In This Plugin you Can make Machines with cauldrons or droppers that take gravel and make sulfur and other IRL minerals and dusts. With This Plugin You Can Use These Things to make auto miners, Hazmat suits to deal with hazardous things!, Grappling hooks satellites likes and etc to kinda make wave points with made torches! or like you can make special foods ( heads ) that you can eat like ice cream sandwiches and whats amazing is that everything here in the crafting table makes sense ( theirs a special crafting table for the plugin to make ) I Love This Plugin so much and if you need more info:Slimefun - Bukkit
Movecraft will definetly be a problem due to CPU consumption, not sure about client side lag. Slimefun looks interesting, but it's dead. OK, that's not the problem since it's about the idea. And yes, something like Slimefun absolutely yes, the exact features have to be evaluated but a good suggestion. Although it's not really suitable for a economy server it's something that can keep people busy.
Movecraft sounds pretty interesting, but it would probably cause a ton of lag... Slimefun, on the other hand, gets a +1 from me. I've worked with the mod before, and I found myself working for hours just to find the materials to get really cool items. It would also create a huge market for exp, because I always found myself not having enough of it.
Although I like the concepts.... this server is mostly vanilla. IMO we don't really need plugins like this on the main server.