So, ForgeWorld has recently introduced these to the background of the system and noted that they're used in ship to ship actions as an alternative Marine assault boat to ThunderHawks and Sharks. Perhaps it would make sense to consider a quick line for the next rules update allowing for their use. Maybe something like:
Space Marine capital ships may be upgraded with wings of Caestus Assault Rams for 5 pts. A wing of assault rams acts like a wing of assault boats as described in the main rules moving with a speed of 30cm, except, that as befits its role as a superbly constructed tool of the Emperors Angels of Death it, like the Thunderhawk, is resiliant to attack and has a similar 4+ save against being removed involentarily.
Quick, simple, and to the point. So, what do you think, worth a few playtests?