Based on a comic set in a steampunk 1889, Gaslight would have kicked off with Bruce Wayne travelling to Vienna to be psychoanalyzed by Sigmund Freud, because famous historical figures are legally required to appear in period pieces. After they chat about a recurring dream Bruce is having about the death of his parents, he returns to Gotham to discover that Jack the Ripper has been busy there. Jack frames Bruce Wayne for his murders, but Bats escapes and confronts the real killer, finally allowing gamers to fulfill their fantasy of punching Jack the Ripper in the face.
And history in the nads.
But the real star would have been the moody Victorian setting, with creepy mist rolling amongst the streetlamps and civilians whom we can only assume would have been wearing nothing but the fanciest hats. While gameplay details are scarce, it doesn't take much of an imagination to picture the potential of steampunk Batman. For starters, there's no way the game wouldn't have included a Batzeppelin, because just typing the word "Batzeppelin" sexually arouses us.
Zeppelins are perfect for Batman, since so many of them end in horrible death and tragedy.