Here's an idea:
Construct your ideal Lex Luthor exclusively from pre-existing non-Luthor sources. Let's say a minimum of two sources and a maximum of 10 different sources (historical or fictional). Also, you can pick and choose which attributes from those sources your ideal Lex would take.
For example,
My Ideal Lex Luthor would be:
2 parts Reed Richards (both theoretical genius and inventive brilliance)
2 parts Victor von Doom (both armor and ambition)
2 parts Tony Stark (both charisma and sex life pre-Pepper Potts )
2 parts Bruce Wayne (both Batgod Anti-Supes prep and physicality)
2 parts Adolf Hitler (both oratory skills and persuasiveness)
10 parts total = my ideal Lex Luthor
What non-Luthor sources would make up your ideal Lex Luthor?