Good question, Gruzewski looks to be elite in that Jeremy Howe type manner but he's not a power forward as you say, I'm actually looking at him as the heir apparent for the Grimes role, he has the closing speed, I believe he has the tank & he has that added flexibility if you need a swingman. Lemmey looked a little bit lost at times this year, he lacked a bit of confidence & his marking suffered as a result, but I'd be careful about judging him on one season alone, last year he looked confident & had a bit of swagger about him. I also believe he played some decent footy in the ressies late this year so maybe things are starting to click. My gut says go with Lemmey because genuine power forwards are hard to find. If you get lucky with this pick then it makes the list build infinitely easier.
Barnett being the top ruck will probably go in the 20-40 range, I'd say very unlikely to be available at our pick. Keeler I've seen anywhere from pick 12 to pick 35 but he's probably gone & I wouldn't even be surprised to see him snapped up in the first round. I think clubs will view Keeler as slightly risky given he can look a little bit lazy with his kicking but he has the complete trick bag & will probably make a decent supporting ruck.