Two issues...

1) Part 61 allows "supervised solo" in a ME airplane for commercial pilot applicants, but does not to my knowledge make such an allowance for private applicants. It would about impossible to get a student pilot insured to solo a twin, and for good reason. I wouldn't sign off a student pilot for that unless he was Chuck Yeager and Neil Armstrong combined.

2) Be careful flying to those business meetings...if the FAA decided you were doing this more for transportation and less for flight instruction they will bust you for running an unlicensed charter op. About the only way to safely do this is if the student owns the airplane. Otherwise you are in a potential grey area.