Well, there's certainly no major MMORPG named maple story that made millions of dollars using a similar art style to refer to, so I'd guess no, it's not viable. :rolleyes:

More seriously,it really depends on what you want to do with the fact that your characters are super-deformed/chibi. For instance, you can tone down the emotional reaction to hyper-violence by making the characters cute. You can also appeal to different demographics by changing your art style. You'll also chase some players away, because chibi art is very polarizing. But there isn't enough of a question to answer “how do I make this work” when we don't know what you're trying to achieve.

Elaborate more on what you're asking and I can give a better answer.

It is an art style. If the developers want the style, or a different style, it is their choice to make.

It is well done in several games, a poor fit or poor implementation in others. The same can be said of artistic choices is every game. Each game is unique, small changes can have massive impact.

If it works for you, wonderful. If not, do something else.