Dig,
I REALLY like the tranny surprise idea.. as soon I read it, I could 'see' the site and I think if done well, could retain unbelieveably. I'd suggest 2 hot 'women', with the primary participant actually being female, so that truly straight porn fans can enjoy a heterosexual blowjob, as well as the subsequent gag.
I also think DaddyH gave you million dollar advice in this thread.
Just my
Good luck, have fun and great fortune-