How about making a type of block that would cost more resources...

Like 10 for 1 block but that would endure like 3 times more..

This could be used to build pillars for bridges..so those wouldnt get griefed or destroyed so fast..
I personally dont like the idea of absolute indesctrucibility..but sometimes a little more stable than those original block would come in handy.

inspired by bridge wars, designed with a twist!

the spawns are very high, connected by two very high paths that intersect at the center of the map, making for quite the hotspot. it's important to hold the center, so build or invade a fort and equip your best scope! pay attention to your surroundings because crossfire is common, and watch your step because it's a long way down.

the spawns are flat and have equally-spaced 1x2 pillars everywhere to provide cover for spawning players.

pics:
http://aloha.pk/index.php?action=dlattach;topic=71.0;attach=40;image
http://aloha.pk/index.php?action=dlattach;topic=71.0;attach=42;image
http://aloha.pk/index.php?action=dlattach;topic=71.0;attach=44;image

download:
http://aloha.pk/files/aos/maps/crossfire.vxl

I'm sure you're aware of this map.

Here it is:
http://www.mediafire.com/?1kt444mkbi3p33r

Enjoy