All students come to nursing with challenges to providing patient care. It may be that they have learning disabilities, mobility issues, or other things that might make nursing care difficult. I had no problem showing a student who was missing several fingers from her dominant hand how to adapt the equipment to be able to insert a catheter using sterile technique, and adapting other skills for all students is just part of what I do. I would also like to say that as a floor nurse I have worked with many nurses who are obese, but when I think about them I think first of their pharm knowledge, or ability to work with difficult families, or who they are as people.
Regarding smoking students - I do tell that they cannot smoke in their uniforms or prior to clinical. I ask that they be respectful of the patients in their care.