I think Evan Bourne is like Eddie Guerrero without the history, rather than Mysterio or Kofi.
Bourne's offence is so much more believable that Mysterio's. The double knee thing off the top rope looks like it hurts infinitely more than the West Coast Pop. His kicks are the kicks of someone with training rather than Rey's weak kicks at the thighs. He doesn't have the lame set up to his finisher, it's been said before, but when other than Mysterio's matches do you see someone land on the middle rope (what especially bugs me is it used to happen, Bossman, Roaddogg etc all used to have guilotine style things on the ropes), in most matches a guy is down within reach of the turnbuckle.
While size again is a big issue, especially against bigger guys, I don't see with guys in the Main Event scene only being about 230lbish (I have no hardcore numbers, but they're not 275lb like the Rock), giving up 50lbs doesn't look so bad, plus he's in proportion unlike Kofi (who looks skinny, because he's long).
He's one of the better sellers in the company, and he's over with the crowd. If he can stick with the company for 3-5 years, he might get a title run, especially if they managed his push well and legitimise him. Maybe a Scramble win? I can't see him being in the same league as Benoit, but I think he can surpass Malenko, his aerial prowess being every bit as entertaining as Malenko's matt work (considering Bourne isn't exactly weak on the matt)