Can you describe what the ring does along with it's limitations please?
From what I have experienced MHR can handle a Justice League game with no problems and no imbalance, which for most supers games is tough to do, but MHR is built with a different paradigm of design than many traditional rpgs.
If you want a list of all the fan made characters people have created for MHR, go to this link.
Lost Files of Marvel! ? Fan-made Datafile Index
Green Lantern (GL) Power Ring (according to wiki): No hard upper limit to the power ring's capabilities has yet been demonstrated; it is often referred to as "the most powerful weapon in the universe."
The power ring's most distinctive effect is the generation of green, solid-light constructs, the precise physical nature of which has never been specified. The size, complexity, and strength of these constructs is limited only by the ring-bearer's willpower; whatever the wearer imagines, the ring will create.
When active, a power ring will encase its user in a protective, life-supporting force field. This force field allows the user to fly, travel through inhospitable environments (outer space, underwater, etc.), and enter hyperspace in order to move vast distances quickly.
Power rings also appear to be highly advanced computers; they are able to talk to and advise the wearer as to various courses of action, as well as act as a universal translator. The ring can also scan for energy signatures or particular objects. For more intricate problems or problems that require a back logged history (Of a planet, person, group, ETC.), the ring connects with the main power battery on Oa which is the "main" computer, of sorts.
Power rings are able to give off electromagnetic radiation of various frequencies. This radiation can be focused by the wearer into a beam, similar in appearance and effect to a powerful laser. The ring is also capable of producing an electrical current...A power ring is also capable of creating fully functional duplicates of itself.
So, you kind of get the point of what the GL rings can do. The others varies on the emotional spectrum they are attuned to, but most are capable of the same as the GL power ring.
At the time of things leading up to BN, the GL power ring had no real weakness. The yellow impurity had been removed but the GL Corps were still unable to use lethal force if necessary. So while they were able to combat yellow lanterns, they could only subdue them and imprison; this didn't always work.
Also, can't forget, the rings need to be recharged after a period of use. The ring worked much like an rechargeable electronic device in that it needed to have it's batteries recharged after the wearer used for extended periods of time.