In the base rules, you can make a swift attack as part of the charge action in Black Crusade, though they errata'd that one out.
Thanks for the answer.
I think I overview these things a little better now. I think there are two points to distinguish: At first, do I want to change the Swift & Lightning Attack to be a Half Action? Second, do I want to go with the new rules to grant extra hits according to the DoS and not make an additional attack roll for each attack.
For the second question, I definitely like the idea. It make the melee attack more comparable to the ranged attack with semi- & full auto.
For the first question, I am not sure. I really could live with the Standard Attack any maybe the Semi Burst and thus Swift Attack to be a Half Action. But for the Full Auto and Lightning Attack to be also a Half Action, I am not fully convinced.
Furthermore, I could live with the old rules from Deathwatch that Swift and Lightning Attacks are Full Actions and can only be combined with the Charge by having the Preternatural Speed Talent. And houseruling that they are still not becoming Half Actions, which makes them just too powerful.
But I do not know. The game system is so deadly, that I do not know if it makes a big difference.