We had five players and wanted to play Forbidden Island this afternoon.
With one rule change we managed to play and win.
Five player rule change:
When a player draws treasure cards they may discard any number of cards to the discard pile. This keeps the Water Rises cards diluted in the shuffled deck and gives you a chance to win.
All other rules remain the same, although I suggest you start at the novice level.
Suggest moving this to variant section.
Nice variant idea.