I am actually very interested in the idea of translating at least one of Gustave LeRouge's book into English myself, and seeing if I could get it published. (Of course, another interesting project would be translating into English, for the first time, ALL of the Fantomas novels.) Does anyone of you have any ideas on this? What publishers might actually be interested in this sort of thing? Or perhaps someone would be interested in collaborating on a translation project, via e-mail or some other means, and splitting any monetary rewards? I would very much like to make some of this literature available in English, but considering the amount of time and work which a good translation requires, I would hardly want to do it without at least some chance of getting published.
John Ashbery also mentions the Gustave LeRouge connection in his introduction to Fantômas (William Morrow, 1986; Bantam Books, 1987). He calls LeRouge "recently rediscovered," but like you I am unaware of any English translations.
As for potential English-language publishers of LeRouge or Fantômas novels, William Morrow reissued the first two novels in the Fantômas series in the mid-80s, but then stopped, apparently after disappointing sales. Given that failure, I doubt that any other large commerical publisher would be interested in such a project. However, there are some specialty publishers that might have greater interest: Fantofriend Tosh Berman of TamTam Books has actually mentioned to me his interest in republishing the Fantômas novels, and you might also try Exact Change and Atlas (both of which focus on English translations of French surrealist writings). I think a proposal for a translation of one of the LeRouge novels might have the greatest chance of success—as you point out, translating the 24 or 25 Fantômas novels that have never appeared in English is a daunting task, which would require immense effort (and if published, expense).
In lieu of a complete translation of the series, Robin will be writing fairly detailed synopses of many of the books which will be posted on the Novels page.