Such a loadout has never been available in AH I or AH II, at least best I can remember, having been here off and on for about a decade or so, so there is no "like they used to be able to".
There's no need for it, either. I suppose, as a compromise of sorts, the 2K# bombs could be made available, as I have seen pictures of them loaded. As stated above, few people liked them, but they were used. A pair of 2K# bombs and the "Christmas Tree" rockets would be plenty of ordnance, and almost certainly the maximum loadout used on any sort of "regular" basis. The case "could" be made that a damage increase due to a diving delivery could be given. For example, a 50% or more increase in damage to shipping due to diving delivery might be something to look at.
I doubt anyone would use such a loadout (as proposed in/by the OP), at least not more than once, even if it were available. You'd need a bomber length runway, and all of it, just to get it off the ground. You'd be so vulnerable that you would require a serious escort, and the climbout/air speed gain would be so long that no one would want to invest the time. The P-38L is already used as a suicide ordnance truck already anyway.