Sanji will fight the strongest Gorosei after Zoros Gorosei opponent, It's that simple. If it's Mars it's Mars if it's Ju Peter or Saturn then that's who it'll be. But some people are using contradictory logic by trying to determine who Sanji will fight by who looks the weakest or least impressive, in their minds Mars seems too strong but they know that he's weaker than Topman and Venus. By placing Sanji against someone who in their minds looks to be weaker than Mars they are effectively making a "Sanji vs Jack" argument without realizing it.
The Sanji vs King argument holds no water since the reason Sanji didn't fight King wasn't because he had wings or was too strong, but because he was Kaido's strongest subordinate which almost always falls to Zoro. The designs argument also holds no water since Sanjis fought characters like Kuroobi and Jabra who were both more menacing in design and personality than Hachi and Kaku. I also don't agree with the opinion that Queen had a goofy design; he was fat, that's about it, but everything else about his design was cool. The only opponent Sanjis fought who actually had a goofy design was Mr. 2, but that was what Oda was going for. Personality wise........they're all serious and stoic, but Oda can easily cook up a couple of gags for them. If you believe Luffy will fight Imu then you believe Zoro will fight Venus.....so you believe Sanji will fight Mars, it's that simple.
