Yes, I wanted to do one of Bowser, since he's on the list of who I want to do for this crossover. And I'm halfway done with the crossover, too (I plan to do 20 total).
While Bowser and the Bullet Bills were pretty quick to finish, the airship made it take longer. HSR typically has human or humanoid characters as playable, so adding a character like Bowser would be out of place. However, because I'm only doing characters that inspire me and Bowser is one of them, it felt necessary to do one of him. Also, splash arts typically have the character front and center and bigger than everything else, but because of how I planned the composition, I had to shrink Bowser down and push him back; I didn't want it to look like he would get hit with the propellers.