Look ahead to the 2010-2011 season for a moment. Pennington has moved on to a team that will give him a shot at starting. Sparano has been proven to be good to his word and Chad Henne and Pat White are competing for the QB job. One of them wins the job, I don't care which.
Henne and White are completely different style QBs - Henne is right-handed, big, pretty immobile and has a gun for an arm. White is left-handed, small, very mobile and has a decent, but not great arm. Which means having Henne and White as #1 and #2 presents problems for everyone else in the offense. If whoever the #1 is goes down, the offensive sets will have to change to play to the strengths of the other guy. Any rollouts in the playbook go the other direction for a righty versus a lefty. The routes that are run will change to play to the QB's differing strengths. Other than Seattle, I can't think of a stronger contrast between the strengths of the starter and his potential backup. And since Seattle picked #4 overall, I'm not sure how well that worked out for them when Hasselbeck went down.
Not saying it's impossible to work around, but it presents challenges.