As they say: "Khorne cares not from where the blood flows"!
Blood for the Blood God, Skulls for Sanguinius!! er...something like that. I want to start a Khorne collection as well to give my BA some classic opponents aside from my Necrons. Just so happens my buddy gave me his 4th edition Chaos army that has 20+ 'Zerkers in it as well as some juggnernaught lord stuff. KDK here I come!
As far as replacing the blood drop, I'm thinking just smooth over where the blood drop was leaving wings and/or purity seals put there. Unless, I can find tiny skulls to mount there. Marines love skulls.
Honestly I wouldn't. My opinions of the model aside, it's just too fiddly a process to accomplish in my eyes when this model exists and you can just find an awesome axe for him:
I'd sooner just paint him whatever way I want using the blood drops and say he's from X successor Chapter of whatever vanilla rules you wish to slop onto the game table. The joys of marines, right?
On the topic of my plog here, I have completely nixed any models from the vanilla 'dex. Sold the hammernators including the painted IF sergeant and am either going to sell the yellow Land Raider chassis I have or repaint it. I'm even thinking of selling my White Scar Captain conversion or scraping it entirely down again to remake him into a Libby on a bike and paint him red. BA or bust when it comes to marines, with the exception of my Deathwing force (shelved pending rules that let them be a standalone army again) and lone squad of Grey Knight Terminators.