Yes, I've nearly got it working perfectly (except the annoying problem with flak knocking back the test aeolus slightly). However, we absolutely need a PrimaryFired and possibly a SecondaryFired (takes a ship, a primary/secondary weapon bank, and maybe a delay) SEXP in order to have decent beams working. I've managed to get the targeting, beam firing, etc working, so that capital ships can be targeted and fired upon as if the beam was a primary. Blob turrets and anti-fighter beams are a completely different story, however, and would require much more than just 1 SEXP to do with any kind of sane speed (1 event must be added per targetable ship). The problem with key-pressed is that you can push the key however many times you want, but the primary dummy weapon will only fire for however much energy you have (50% energy is drained with each beam firing, so you can drain your engines (the aeolus is given afterburners, too) in order to increase beam output). The result is that you will be getting free beams...
Why all of this? Currently, player-fireable beams can only shoot straight forward. For a better capitalship style play, they need to be able to fire on targets like true turrets would, meaning broadsides would be more effective.
Optional SEXPs:
1. GetTargetedShip (to be used as a data field; this would make it possible to use anti-fighter beams and it would be a ****load easier to FRED in general)
2. GetLoadedPrimary / GetLoadedSecondary (checking the primary/secondary type would allow for swappable beam types in the loadout selection screen. There is simply no way to check which weapon is installed as it is...)