This is a long and complex story @aussieninja. the main reason why the argument is made that witnesses are paid so much more than their operating costs is due to the risk of potential corruption payments for manipulating the chain.
If @oracle-d was a top 20 witness, we would give 50% of our witness rewards to projects. I am not sure why other witnesses don't do this.
Ah, the anti-corruption thing does make sense. I've often wondered if the speed of the Steem blockchain also makes it less secure... given that Bitcoin and other blockchains rely on a number of nodes reaching a consensus on the transactions.
Thinking about it more, I think what I'd like to see is a witness portal that lists all the witness information including their other projects and their donations to the blockchain development/WPS. That way the witnesses donating more to the development of the whole blockchain should be rewarded with higher rankings.
In regards to the question you raised about logos and sponsorship. The competitions on TV are extremely strict about logos or anything of that nature. Last time I competed I had to bring 4 t-shirts for them to choose one, and people had to tape up or colour over with a marker any Nike, Adidas or New Balance logos, etc.
The smaller competitions don't have rules though. They're not televised but they all broadcast live on social media. I've got my own Aussie Ninja top, but I'd be open to include a 'powered by steem.ninja' type thing if that's any interest to you.