Vanilla Minecraft has a middle-click function which allows a block of the same type that is highlighted by the player's cursor to enter the inventory (I'm not sure if it's only in creative mode, but it is very useful).

I have seen modded expansions of this such as with mods like Pistronics and OpenBlocks - certaion blocks from those mods have NBT tags (the properties) which are also applied to the block the the player receives upon middle-clicking.

I would like to see something similar to that (just to aid creative building; whenever I do something that I cannot do with WorldEdit, for example, lining a cave with lights that look like other blocks, I have to place the Carpenter's Blocks, and then apply the textures and the glowstone dust for each block - it does take a lot of time).

--EDIT--

Speaking of properties, how about a fire-resistance property? Some people may make a build that involves stuff like acacia wood and lava (would look nice). The fire-resistance property would prevent the wood from burning and disappearing. The blocks would also be unsuitable for use in a furnace.

And speaking of furnaces, why not add a feature which allows Carpenter's Blocks to be used as fuel in furnaces - but whenever there are things added to the block that are also flammable before being used in the furnace, they extend the burning time. This could allow compact fuels! (Anything that has been added to the block and will not burn will just have to be ejected by the furnace - or it could be used as the material that it being smelted; for example, a Carpenter's Block that has been given the texture of an iron block could be split and the end result would be the creation of a steel block.) The energy value and burning time would have to vary with the amount of space that the Carpenter's Block takes up (a prism slope wouldn't burn for as long as a whole Carpenter's Block).

1. Storing NBT data for pick block is interesting, and I only just looked into it. But, the blocks in this mod aren't meant to retain data when destroyed (or in this case, pick blocked).
2. Fire resistance is entirely dependent on cover material, and further alterations to a Carpenter's Block are typically cosmetic only. Fire is and will remain a threat to wooden structures.
3. Again, relies on the NBT tag data which is not stored for these blocks.