I comment on parts of my thinking in various change logs so much of this is already out there but I thought I'd put it in this form.

First the problems:

• Large numbers only make a small difference in pvp
  • Nothing for less skilled players to do to help
• Little advantage to defending an established location
• Ease of block placement based griefing
  • Lava bombing
  • Diamond Reinforced obsidian (yes, I know about acid blocks)

Goals:

• Simple
  • Must be as emergent as possible
  • Must be easy to learn and understand
  • Minimum number of new commands
• Fast
  • The new mods must not slow the server down

My proposed solution:

• Mod one: Bastion
  • Protects an area from block places
  • Use
    • Place a gold block
    • Reinforce it
    • Only those with access to the reinforcement can place blocks within a radius 5 cylinder starting at the top of the gold block.
    • Every attempted block place removes a level of reinforcement
    • When the reinforcement reaches 0 the block is destroyed
  • Problems
    • Has the potential to be inefficient
    • Block placements can be spammed quickly possible a need to change the blocks placed to reinforcement ratio
      
    • May be unclear to new players.
      • Blocking breaking and dropping item rather than just disappearing may help
    • Doesn't address many problems
      • Really only partially makes established positions easier to defend and potentially helps stop block placement griefing
• Mod two: GateKeeper
  • Very simple, allows for a interaction with levers, doors, ect. Only when someone has a signed item
  • Usage
    • Place chest with a copy of the printing press produced pass inside
    • Put some intractable block above.
    • Reinforce both with same group
    • Now the intractable block can only be interacted with by
      • A member of the group
      • Anyone holding a pass.
  • Pros and cons
    • Doesn't solve many problems.
      • Just allows for access to fortifications
    • Very simple (for a player)
    • Probably fairly lightweight
• Mod three: SiegeFactory
  • This will be the most controversial.
  • Repairs blocks
  • Creation
    • Factory similar to all other factories
    • Recipe would need to be very expensive think stacks of diamond
  • Operation
    • Price scales based on number of block brakes
      • Something like a stack of iron blocks and three stacks of charcoal needed per 3 attackers per day
    • Even without block breaks it will still take a constant supply of charcoal and iron/diamond/stone
    • Only repairs the area protected by Bastion and the Bastion Blocks
  • Pros and cons
    • Less than simple
    • Possible hard from a development/server load perspective
    • Gives a much more interesting dynamic to towns fighting. One Where we could have sieges trying to starve a city of supplies so invaders can break in
    • Gives something for less pvp oriented players to do to protect thier cities.
    • Helps protect established positions

I've actually started working on a prototype for the first mod I mention. I'm doing it mostly as project to teach myself how to code Bukkit mods so keep in mind it's probably not going anywhere, but here's its source and here's a quick video of it in action. (The little bit of player based logic that this has was disabled for this video) Also as I kind of lost the source at one point and got it back by decompiling the .jar you may notice some strangeness