Why not a token? I can't get your point I agree that they don't have a real value until they are listed in exchange, but some of them help in
solving real world problems and
the complete usage of blockchain technology in various fields.
If such a thing is implemented, almost all the spammers and bounty managers would join and conduct bitcoin campaigns which would deter the quality of forum even more as almost all the bitcoin campaigns (excluding chipmixer) demand a minimum post of 20-25. Spammers can't even post 10 meaningful posts per week, how can you expect them to post 25 good quality posts?

Nowadays campaigns are managed by Newbies and Jr.Members who doesn't even know how the forum works or doesn't know to evaluate posts. Allowing Copper Members, Full Members and up to create a topic in Bounty section may help a bit. Very few bounty managers look for the post quality and actually read them. Rest just check the number of posts created and award them stakes.

Bounty managers never consider the spams generated due to their poor regulation and management. They will not even mind using it?

If all the bounty managers were like you there would have been quality posts and real discussions flourishing all around the forum. Forbidding signatures is literally a bad idea to consider. They will severely reduce the traffic generated on the website and there might be losses on theymos side. On the other hand, a similar forum would be created and all the spammers(traffic) will leave this forum forever. Moreover theymos said he has completely ruled out this idea and will think of it only when merit system fails.

Increasing the merit requirement of Jr.Member to 10 and Member to 50. A member will receive 50 merits only when
1. He has good knowledge in bitcoin or
2. He understands how a forum works and makes some decent posts or
3. A prolific writer

Not only altcoin campaigns generate spam, bitcoin campaign also does. Hence reducing the minimum post count to 10 or pay per post similar to chipmixer would work.