1. You mean like how he did that to Zoro, right? And even if Sanji's feet are covered in stone, is that supposed to actually stop him? The man who can kick buildings and shatter steel with his foot pre-skip is gonna be stopped by stone boots?L0l No Pica has already shown the feat of manipulating the Golem once Sanji lands his feet get covered in stone... Also how is Sanji going to murk him in cqc when he not only has the entire Golem to help him and he can merge with it if it gets to rough... Having the Golem punching it's self means nothing when it can rebuild...
2. When Zoro landed on the Golem, Pica immediately went to confront him directly. Pica stopped moving the Golem completely. Why would it be any different with Sanji? Sanji completely outclasses Pica in close quarters.
3. You're saying Sanji needs to destroy the Golem to defeat Pica, and now you're saying the golem being destroyed means nothing? If Pica tries to attack Sanji while Sanji is standing on the golem, then he just does the cook's work for him and makes it even easier for Sanji to fight him.