I wholeheartedly agree! In fact I was thinking the same thing for the last few days. There seems to be 3 important factors in beam weapon design: Caliber, Fire Rate, Range.
These seem to be very rigid, very dependent on caliber; creating a sort of linear weapon progression. You just use the biggest caliber you can, at the longest possible range. When comapred with missiles, the lack of flexibility is quite apparent.
Especially since beam weapons are quite small in general. A single 80cm laser masses 1250 tons, while a size 100 launcher is 5000 tons. You can load a lot of 80cm weapons on a reasonably sized ship, making smaller weapons much less attractive. Reactors do eat a lot of mass, but mostly at larger calibers (30cm and up).
The design philosophy of Aurora is heavily marked by a focus on diversity of playstyle. Having pros and cons to using smaller/bigger weapons in general would aid that objective.