Another answer to this problem, would be to take a well known DC character and develop his/her character in the L&C universe. Then "spin-off" the character from the show. Then crossovers would be no problem.
This happens with spin-offs all the time (think CSI shows - for example).
I've done this in my story (Missing Lois), but alas, you have to wait until Chapter 8 (I think) before he shows up. Hope that wasn't a spoiler.