The docking bay available now can house a fighter or bomber for 300 cargo. Largest freighter has 650 hold. Docking modules capable of housing a freighter definetely will need more hold space. If we calculate with a 500 cargo hold need, the extra space you can get is 150 per module + freighter (250 if the larger module needs 400 hold space), plus the profit is split between the 2 or 3 ships. That's plus 50 cargo unit/per player (half - one million credits if we calculate the most profitable commodities). I think this does not make a very huge difference.
Other use of freighter-housing docking modules might be helping the lower level players transport their cargo more safely.