As a Data Analyst/Manager I can tell you right off the bat that this would not work because of
  • Time invest: Both games are going to compete heavily for time. Making it so that most people don't opt for this package option. And a lot of those that do will eventually drop this package when they notice the time investment conflict.
  • Conflict: This puts the FFXI "development/operations" employees in a very dangerous position where they have to deal with the uncertainty of how successful this would be. This is a very hard sell for CEOs and investors.
  • Working environment: This might endanger the health of FFXIV, creating not only service conflict between FFXI and FFXIV but also in-house conflict between the teams. This could ruin working environment morale and culture.