MyBB Community Forums

This is certainly one of the most important parts of a forum. I know MyBB must have it, most forum platforms do. I know vBulletin has a full customization of the signature including BB sizes, images, links, colors and more and can be changed for each user group.

Where do I find this option?

Mybb doesn't. You'll need a plugin to stop links.

This is the closest thing I can think of: http://www.mybbcentral.com/showthread.php?tid=1670

This limits the use of signatures completely until a certain post count.

There is also: http://mods.mybb.com/view/automatic-signature-removal

Which does the same as the one above.

I wonder if this simple, yet powerful feature will be included in the next update. Making links only available for VIPs will make more people buy VIP (user group).

If enough people suggest it, they may add it in. However a simple plugin should suffice. Check out what Conor gave you, those should work quite nice.