Cowen isn't a speedster. Granted, his mobility is much improved. However, if you're not a fast guy, you have to have high hockey IQ, which is something a guy like, for argument's sake, Stone has (Heatley being the champion of slow but in the right spot) but IMO Cowen does not have high hockey IQ, nor is he a finisher. Cowen's role on the team right now is to be in the right spots defensively. That's it. And he can't even do that properly seeing as he's in the press box right now. There are other reasons why he wouldn't be a good forward (he also isn't playing nearly physical enough to make up for other deficiencies, it's not like he has good hands or great vision...) but that's the biggest one IMO.
Even Condra, a guy with no offensive talents, gets by because of his strong hockey sense.