Let anyone create a link to sell the Lego pieces for their own creations and get a percentage!
Let anyone create a list of pieces at the Lego shop, and a single link to place them all in the cart. Those who use the link get a discount (something between 1 and 5%) and the link creator also receives a small percentage (also something between 1 and 5%). In this way, anyone can advertise their creation, with instructors on how to do them.
And those who want to build it can order the pieces with one click. They can also modify the list of pieces, to eliminate some elements they already own (they should not feel treated unfairly).
In this way, anyone will be able to partner with Lego. Lego Ideas can still make its competitions and produce its boxes, but this will explode the number of Lego pieces sold by MANY orders of magnitude. And the revenue will go through the roof.
For example yesterday I spent a long time going through the Lego shop to buy the pieces for something I found online. How many gave up before? The web is full of lego creators. Not just Lego Ideas, but also YouTube. If creators knew they could get some money, wouldn't they list the pieces and make a link to buy them?
While right now many creations do not even list the pieces, making it nearly impossible to recreate them.