I would keep 6 WR's and mine would be: Baldwin, Lockett, Richardson, Kearse, Williams, & McEvoy.
Kasen Williams hasn't been on the field much this preseason, and I understand the people thinking his spot is in jeopardy because of that, but in my opinion he showed enough last year that he was already penciled in for a spot this year baring some amazing play by a few other guys. However, I don't think any of the guys vying for the last spot or two really shined this year. Maybe Goodley, maybe. Kasen offered good depth as a fill in WR when called upon last year and was MUCH more physical last year than anything I've seen out of the guys this year. He was pretty good as a gunner too on ST's which is something to consider.
McEvoy I actually hate at WR. I just feel like it's not a good fit for him, but I think the coaches were right to put him there for now as that's his best chance to earn a spot on the current roster. I like his physical tools, he's got a great size/speed combo. I also like his versatility making him a great guy to have active on game days in case of injuries. He could be an asset in ST's and that's why I'd keep him as my 6th WR for now. Hopefully you won't ever need to use your 6th WR as a regular in the offense. That guy should mostly just be a special teams player which fits McEvoy well right now.