Couple suggestions from me:
For server admins:
An option to Teleport to a players brick. For those times when you see bl_id 1234567 has 800 bricks and you have NO clue where it is.
- also +1 for the selective load/save option (somebody on my server lost their build yesterday and I had to spend 20min retreiveing it from a previous save).
Non-Admins:
Draw a box on the screen to select bricks.
Normal control+click to select multiple bricks.
FULL undo support -- "oops I didnt mean to delete that tower"
Standard copy+paste functions.
ex: select some bricks (via whatever method). hit Control+C to copy, then Control+V to paste -- then have the paste function AUTO PLACE a temp brick, and from there it behaves like duplicator.
a "simple" ability to pickup and move a build.
De-spamming builds is a good idea. here is an approach to consider:
pass 1, change 1x1 into 1x2.
pass 2, change 1x2 into 1x4, or 2x2 depending on whats around
pass 3, change 1x4 into 1x8, or 2x4, change 2x2 into 2x4.
and so on... (assuming you match bricks by color and dont touch anything with an event).
that works well for horizontal de-spamming.
then its just the same for vertical -- find stacks of 1x4s or 1x1s and change them to 1x1x5, or 1x4x5
slow - yes, but it can work well to cleanup spammy builds, and its not like you will be using it constantly.
And lastly - some client-side building aids:
macros or keybindings that will feed plantbrick() and shiftbrick() commands to let people build stuff. ex: makeline(5) - takes whatever your temp brick is and makes a line of 5 of them directly in front of you. or: makecircle(5) - makes a circle from your temp brick.
I have started on this already, and its a lot of fun to play with (until some noob does /makecircle 5000 )