Many of the names on this list were already old, (Washington, Reagan, etc) so adding more years to their lives wouldnt have much mattered.
Gus Grissom, Ed White, and Roger Chafee were three who could have been productive.
Any three servicemen who died since 9/11. They would be important to a couple generation of their families.
Ahem. George Washington was 67 years old and some of us are older than that...