Well I look at this as the BPA, if he's mobile thats just a bonus.
One thing though, if its truly a running QB, you will want to draft a running QB about every 3 years or so......you can't have a running QB with nothing behind him either developing or ready to play cause of injury (which is why what the Skins did was smart). A pocket passer gives you the opportunity to develop other positions cause the likelyhood of him being injured is less and his career will be much longer. A running or mobile QB might have a shorter shelf life, but the options he can give a team can't be denied in the running game, play action, and especially empty back sets (something not enough teams with running QBs use, it would be deadly).
A very mobile QB brings alot to the table, and it shouldn't be ignored how much his mobility can help the run game and the versatility of the offense. I always hear that no running QB has won a Superbowl.....well that will fall sooner or later now with them finally being accepted in the NFL, and I have a feeling it will fall then the flood gates will open with mobile QBs winning it a whole lot.