Here are some ways for Nintendo to boost Wii U sales:
1. Pull the normal Wii from retail shelves.
This would be really stupid, given how profitable that system must be at this point. Nobody's choosing between the two systems anyway.
2. Discontinue the white basic model Wii U.
How exactly would this increase sales? Removing the cheaper option seems like it would lower sales, not increase them.
3. Cut the deluxe Wii U down to $299.99 (price cuts worked for the Vita).
This would likely help, though the sales benefit for the Japanese Vita price drop hasn't seemed to continue past the first week.
4. Change the name of the Wii U to the "Nintendo Stream."
This is an awful idea for so many reasons. For one, changing the name of a console after it's already been released is a marketing nightmare.
5. Launch the most advanced marketing campaign affordable to convey what the system is to consumers.
This is the only really good idea you listed, and it's baffling that Nintendo hasn't done this yet. Maybe they're waiting for the second wave of games.
6. Allow third party developers to take 90% of the profits on eShop sales to boost suppot.
This might work, and it might just keep the same level of support with less money going to Nintendo. It kind of strikes as a desperation move, and something Nintendo can never really walk back from.