Playing an observer isn't the most gratifying experience as it currently is. As a result, alot of people aren't interested in filling that role, often leaving the commander useless as well.
A way to combat this, could be to make the commander viable, when no one has picked observer. Of course this would have a downside to not be overpowered. For example, since the commander has to call everything in himself, the time it takes between ordinance calls could be increased by 50%.
Then a team with no observers could still get the benefits of fire support, albeit at a slower rate.