Why not? Is it integral to have every single thing you want this guy to do in one character? You can still keep your general idea of satoshi at the core it's just you can put somethings like being the heir of the einzbern to some other character or so such. While many characters do have some very varied adventures it's either after several dozen volumes, or after passing through many writer's hands that this happens.
While I agree that a main character should get a lot of focus in the story Satoshi seems to have a lot of things with him as the focal point. Give those things to somone else, share the plot with other characters.