Ever wanted that one elusive piece that you could never get, either because it was exclusive to a single set, or is simply out of production?
My idea is something of a parallel to the current LEGO minifigures line, only rather than there being full minifigures, we have individual pieces, which are too niche or rare for the Pick a Brick or the casual LEGO shopper, but are of far greater interest to MOC'ers or otherwise. The other nice thing that comes with this is the ability to release new, alternatively coloured brick moulds into circulation in colours that are typically rare or hard to find - for example, lime green connection joints or metallic gold armour pieces.
To illustrate the example, say that these pieces may be released into circulation - I haven't quite figured out the best way to choose the bricks, so either it is decided by online suggestions/polling or the LEGO company uses their best judgement - such that there are ten random bricks to a pack of a possible twenty. However, by far my favourite option would be to state exactly what is in the pack, on the pack, and have different bricks in different variant packs - in a manner similar to that of Yu-Gi-Oh, only without the randomness and without the inevitable disappointment. For example, we may have the following in a pack:
1. Basil the Bat Lord's Helmet from 6007 Bat Lord
2. 5x8x3 Cockpit from 6195 Neptune Discovery Lab
3. BIONICLE Kanohi Vahi from 8715 Ultimate Creatures Accessory Set
4. Golden Greatsword from 8781 Castle of Morcia
5. Grappling Hook from 6462 Aerial Recovery
6. Three-Axle Connector Joint from 30057 Anakin's Pod Racer
7. String Reel Winch from 6441 Deep Reef Refuge
8. Vezon's Cape from 8764 Vezon and Fenrakk
9. Technic Spring-loaded Cannon from 7714 Golden Guardian
10. 2-Katana Scabbard from 7570 The Ostrich Race
This is just an example of what could be in there. Customisation should be important - the bricks should not just be standalone pieces. For example, the scabbard and weapon go with almost any minifigure, and I could see the Vezon cape and cannon being useful for Hero Factory upgrades or some such. These would be listed on the back and it would be possible to buy more than one pack, in the same vein as the current Ninjago booster packs.
I mentioned coloured pieces earlier - these would be nice to have as well, mixed in with the more standard "rare" pieces - there are some colours that are extremely nice, such as teal, which become a bit limited if you don't have the complementary green or blue pieces to build the set. So, a grey would be, while boring, more universal in some situations.
So yes, that's my idea. It strikes me as something that would be very gratefully received, without being a too taxing investment. Rate, hate, critique. Might add more explanations later if anything is unclear.
NB. As per the "don't suggest releasing old products" rule - before anyone says anything, I don't believe that this infringes it per se, since these aren't old sets or models, just parts, and the potential to make them genuinely new either by recolouring or releasing new moulds alongside the old ones is always there.