AAG's original plan was to have the 3 wholly owneds each operate an individual fleet type. Envoy would operate a fleet of e170/175s, PSA would operate CRJs (700s/900s), and Piedmont would operate the dash (until it retired) and a fleet of 50 seat RJs (most likely e145s). Each operation would aim for a fleet size between 60-80 aircraft. During the negotiations and several failed attempts by AAG to bring concessions to Envoy this plan was changed multiple times. At one point the plan was to have Envoy as the single route to flow to AA and they would operate a fleet of around 170 Embraer a/c (e145s/175s), Piedmont would either be closed or merged with PSA or Envoy.

The current plan should PDT pass the LOA is to place 50 seat RJs at PDT shortly after the LOA is passed and to eventually deliver the 20 e175 firm orders and 20 options to PDT starting in 2016. PSA will get Envoy's CR7s and Envoy will shrink as their pilots flow to AA. The net result being 3 somewhat equally sized wholly owned regionals, which if staffing becomes more of an issue, can be easily merged and downsized further. All of this could change again if Envoy and AAG get back to the table, although it seems unlikely now . Keep in mind the TA was agreed to while AAG was still at the table with Envoy. This explains all of the conditional language in the PDT LOA.

This is just my theory anyway. Probably should have started out with that.