One approach would be to write some custom code which hooks in to the DocumentEvents.Insert.After global event which would update the auto-generated page alias into the format you want it to be i.e. "first-last".
Note I've used a hyphen "-" to seperate the first and last name as you wouldn't normally use a "." in a URL other than for a file extension at the end of the URL.
If your staff page type has fields for first and last names you could use the values of these fields to construct the new page alias instead of having to perform a substring on the email address to get everything before the "@" symbol.