If the signature needs to be disabled, that should be done for all the members. There were many high ranked members involved in merit abuses cases. Especially, the high ranked members who got the rank by default should be treated same as a newbie.
This completely ignores the fact that most high-ranking members didn't join bitcointalk to shitpost for bounties. That's a relatively recent development, and by limiting or prohibiting signature advertising in the lower ranks, it discourages people from making new accounts and ruining the forum with shitposting.
I don't see a lot of Heros and Legendaries making a living here by writing complete nonsense. That's almost exclusively a noob issue. It also sounds like you're extremely butthurt about the merit airdrop back in January. That happened because I think Theymos realizes the higher ranks have earned their way to those ranks. In addition, most of the merit abuse I've seen has been with the lower ranks, which is not surprising since
they're the ones who want it the most.
That strengthens my suggestion. If they are so rich and busy with their work, they do not need bounties at all.