Is it possible to hide an account from the login screen where you can see all the users?
sudo dscl . create /Users/username IsHidden 1


Replace username with the username of the user you wish to hide.
To unhide the user, replace 1 with 0.

You can still log in as a hidden user by pressing ⌥↩︎ on the login screen, then entering the username and password.

Additionally, you could delete each account and leave the home folders alone. Changing the permissions to let your user read them is pretty straightforward an if you ever want the other users back, add the same short name and system preferences will give the user back permissions on their home folders again.