2006 Colorado Rapids stats:
http://www.coloradorapids.com/stats...S&op=Search&form_id=mls_stats_individual_form
If you're too lazy to click, Beckerman tied for the team lead with 7 goals, playing as a CM. Until he played under Kreis at RSL, he didn't play a dedicated DM. In addition, he still plays around the box enough to net 3-5 goals every season. Compare that to a more of a true DM, like Seattle's Alonso, who hasn't scored since 2012.
Remember, Kreis' midfielders are expected to do everything well, and cover for each other. The CDM will hang back and usually act to disrupt passing and win the ball back, but he's also expected to be able to distribute well and make runs forward when they are available. He can do this because the other two CM are expected to also be able to drop back when he does so, and assume the CDM role temporarily. They just need to be smart soccer players who know how to function as a unit.
If Poku has some tenacity, and is a strong distributor, he can absolutely be moved to CDM in our formation.
EDIT: To pile on, Poku only scored 3 goals in 20 starts and 5 additional appearances as a sub last season for Atlanta. We aren't talking about a prolific goal scorer, just a good athlete that Atlanta was playing in an attacking position (possibly out of place, as he said he played defensively growing up.) At just 22, he can be molded - Beckerman was 24 in the 2006 season cited above.