Not necessarely:
Huh. Not sure why I thought a 10-ton fighter couldn't mount a turret particle beam.
But it's unlikely you need to work in all your fighters externally at once. Maybe just having such full hangers for 5-10% of your fighters may be enough, while the rest can be in smaller ones (and so not able to be externally serviced/repaired, but fully opperative otherwise), or even externally in Docking Clamps (1 dton per clamp, as per HG page 46), so forfeiting the need of the launching tubes (I asume all the clamped small crafts may be launched at once, as can all the drop tanks that are also so clamped)...
Now that you mention it it, a 300 ton ship I designed for GT that carried fighters had all but one in bays (listed volume) with a proper hanger to allow one to be worked on at a time.
I will need to reread the launch tube rules to see if this will be an issue.