I can get behind that.I personally think Omni is solid, but there are a few issues I see. He is quite straight-forward and linear, so he can be predictable in a sense. He is also a bit more kameo-dependent than the average character, though I do think he meshes quite well with Jax, Sonya, and Kung Lao. Finally, I haven't reviewed the frame data recently, but some of his normals are a bit slow/sluggish. Ultimately, I think he's somewhere between mid tier and maybe upper mid.
Not sure on the Kameo options other than Mavado though, as I haven't really seen the Jax or Sonya parings. Mavado being an "auto confirm" off of everything Omni-man does feels very strong. Armor, clap, his 12-frame mid B12, 222 string. . . all lead to full combo on hit. F3 Jails into the +9 on block mavado hit-grab. Speaking of that, its a great tool to disrupt keep-away. One hit (usually on someone backing away or starting to throw a projectile) and Omni-man is back right on top of you.
Linear and predictable, Kameo dependent and lacking any true mix-ups are the negative marks I'd give him.