Taking Note on the Website of a Classmate's Death
A simple solution is to change your classmate's address to "Deceased" - that will show up in the Classmates List page without any other change (at least, if "address" is currently displayed in your list).
You might also create an unpublished check box in the profile - if checked, then it could show that the classmate is deceased in your Classmates List page. I've done something similar by creating a "Radcliffe" box and a "Lives Near Boston" box in the profile.
As for creating a profile link to your In Memoriam page, you can create a URL field for that in the profile. A living classmate may write a web address there; then when a classmate dies, the website administrator would just replace that with a link to your In Memoriam page.