If the soul thinks on its own but only gets to communicate to other souls via a body, you get the same observational consequences. If souls have their own language of thought, then thinking might still be mediated by language and yet that mediation not require a body.

I haven't said "thinking is mediated by language, therefore souls need body to think". I have said "if souls need body to understand and actively use language, then souls need body to think".

One question you might want to ask here is whether you are interested in going after the best possible soul theory or going after the probably-confused beliefs of typical soul-believers.

To answer your question reliably I'd need to know what do you mean by "the best possible soul theory". If it means "the theory which is most carefully crafted to avoid contradiction with observational evidence", then I am probably more interested in beliefs of typical soul-believers. Moreover, I wouldn't call the overfitted soul theory "best" and the ordinary beliefs "confused"; this creates impression that theology clears up confusion of folk religion. My opinion is that theology only replaces simple confusion with elaborate confusion of greater magnitude.

I wonder whether anybody would start believing in soul if the idea was first presented to them in form of "the best soul theory".