WI Drusilla had not died from a surfeit of buggery ?
With his sister probably becoming his wife, and vaginal sex producing a son (which he was planning on), would Caligula's reign have seen a reining in of the excesses, and a step back from the stupendous depravities ? Brother-sister marriage had been common in many Eastern states (Pontus, Egypt to name two) and whilst a shock to the Romans would not have been one that could not have been overcome. A son and heir from his beloved sister would have provided that blending of blood that he seemed to crave, and maybe the later excesses, many of them resultant upon his grief at her death, would not only have been eased but have been diverted into more fruitful endeavour ?
Best Regards
Grey Wolf