I feel like cosplaying and role playing are fairly different, and I personally oppose to combining them.
Cosplaying is purely dressing up as your favorite character. Acting or speaking like them, while it does add to the fun, is not required. Also, cosplaying cannot be done online.
Role playing is taking on the personality of a character and giving their reactions to the different scenarios of a storyline. Dressing up like the characters can be a fun addition if the role playing is verbal and in real life; but the virtual world where thoughts and actions are also described in detail is quite different.
I would understand if the two were combined. They do have enough in common that I would not object too much.
Now I do hope that someone starts this; I would very much enjoy partaking in any role play…
To the Library!!!