I want to make a big multiplayer Technic town, with a power grid and what not. Make it Hardcore so employers have a reason to give "health insurance" to their employees.
Make it have sectors of the town devoted to different things. TSRNPP (Totally Safe (Really!) Nuclear Power Plant) would be staffed by skilled nuclear engineers.
The friendly neighborhood Refinery would be the place where the Miner's Guild would drop off raw ores to be macerated, forged, and made into goods by the staff.
The Museum of Wonders and Weird Smells would be a safe haven for those both dabbling and experienced in the magics of bending Thaumic Energies, and those who have the intelligence or wealth to use Equivalent Exchange techniques for the good of the town.
The Creepy Blinking Laboratory of Seizures would be for the redstone (and by extension, RedPower) engineers. Huge building with lots of explosion-proof floor space, and would be staffed with janitors to deconstruct and recycle unused mechanisms taking up space.
Not sure if even a quarter of Technic Mods have multiplayer support, though. Neat little thought, though.