I made this for our server "Slaker's Paradise" for one of our worlds. It is hollow underneath with stairs leading down. Under it is a level 30 enchanting table. Also located next to the enchanting table are the basic crafting needs (furnace, crafting table, brewery, cauldron...etc. ) For our server, we will be putting up a shop on the walls near the crafting area. I have ensured that this is a well lit spawn.
The base itself has lots of room for many portals if desired. On each side of the spawn base are rooms for portals as well. These are accessed by stairs from the outer ring. In the center would be the main portal.
If you don't want to use it as a portal/spawn hub then use it for whatever you'd like!!
Please let me know in comments what you think!
schematic and screenshots posted below