At the same time Dynamite Entertainment had the Phantom license they also had the license for Doc Savage. Stan Lee labelled Doc Savage as the forerunner to today's modern hero's.
Doc Savage first appeared in American pulp magazines during the 1930s and 1940s as a doctor, scientist, adventurer, detective, and polymath who "rights wrongs and punishes evildoers".
It all sounds familiar and makes sense why Dynamite Entertainment would explore a possible crossover.
Brent Schoonover (interview here) was asked to create a cover and then some interior art to pitch the idea. Between the inking of the cover and the colouring it was obvious it was not going to go any further due to copyright issues.
It never went any further and all parties moved on. Would you have been excited to see it?