I really don't think I could twist a Rubik's cube at my age, not for 300 solves a day.
Here's three bad suggestions:
(1) Make up a list of better cubes, say all the cubes that have set world records for 3x3 in the last 8 years.
These will be printed on business card size card stock by the companies that export "knock-offs" to the United States. They will also include their own internet address on the cards.
Instead of including one such business card in a shipment, they'll include a dozen or two. Cubers carry around the cards and when someone asks about the cube, they hand out the card.
The result is more business for world class cube companies, more people speed cubing, but I wouldn't bet that this would decrease the number of Rubik's cubes sold.
(2) Make it illegal to use a cube with Rubiks colors at a WCA competition unless it is a Rubiks cube. This is what Seven Towns is literally asking for. The result will be that the speed cube makers will be forced to ship cubes that do not infringe. Eventually Walmart will sell speed cubes. This may seem unpleasant but it could be forced on the WCA by a letter that could be written at any time. And if such a letter arrived, it wouldn't be as convenient, if the WCA plans it, they can make the change to the new rules happen 12 months in the future instead of "henceforth and immediately".
(3) Have the WCA define a color scheme that definitely does not infringe and copyright it into the public domain. Then require that all cubes at WCA meets use this color scheme. (People will still be able to use half brights or flourescent etc.) The result will be that the speed cube makers will be forced into selling cubes that do not infringe Seven Towns. Eventually toy sellers in the US will start selling them. Again, this eliminates the sword that is hanging over the WCA.
So Seven Towns hasn't sent that letter to WCA yet. Maybe that's due to the fact that there are no Seven Towns cubes suitable for speed cubing. There's been rumors that Seven Towns is working on a speed cube. If those rumors are true, the logical thing for Seven Towns to do would be to ban infringing speed cubes by writing that letter to the WCA. As someone said here, what would speed cubers do, quit buying Rubik's brand? I don't think that's a real threat. From the situation they're in now, it's not possible for Seven Towns to do anything that would reduce the number of cubes they sell to speed cubers.