Someone mentioned "trying to advertise with banner". The one and only usage of signature banner is to advertise, however it needs to be done within certain guidelines. I did have a siganture banner and it was related to me selling GAds threshold accounts. However, since around 1 year, people are not too successful with GAds. In my case I am still having good success, and I can if I want to , even right now, this very moment, change my signature banner and use it to sell GAds accounts (BHW rules compliant). However, I do not have the need to do so, so I am not. I have my way of utilizing these accounts and a few old-time buyers who consume in regularly, so for now I do not sell. And in future, if I decide to sell through BHW in any way, it would be as per within BHW rules.
Understand this forum, please, it is BLACKHATworld. OP's type of suggestion if implemented would lead to chain of events which will drastically reduce the number of BHW sales threads.
It is not about me, I am fine. I know even how to run a GAds search campaign itself, to sell even GAds threshold accounts !!! I know how to attract my targets even using YouTube, Favebook, etc ... All that is not needed for me, I am already going good with my thing.
So, it is NOT about me, I am thinking about ALL sellers and all forum stakeholders and how the future would be, this suggestion is not good for a forum like this.
Incase of services that are "shrinking", they will go away from BST sales thread in an "organic" manner. And that is why now, there are less and lesser BST threads for GAds threshold accounts. So, no need to do anything about it. The system is already in place naturally and organically. And newer threads will come with newer services, as the world of IM keeps evolving. Placing the restrictions that OP suggested, may even restrict possibility of some future sales threads related to newer IM stuffs to reach BST sales thread.
Bringing rule suggested by OP, will trigger events for people requesting some other services to be banned as well from BST or signature banner and it is not good for the forum, in my opinion.