Here is my plan for the Phoenotopia: The Lost Journey.
Partially redrawn graphics for the legacy areas and features.
The Unit 66, the final boss in the legacy Flash version, which was originally accessed by defeating the Master Computer, is replaced by the Great Boss of Earth, the pivotal boss that diverges between the legacy chapters and the new chapters. The latter boss is also far behind the midway of the world, as the world is more than twice bigger than the former!
Greatly expanded world (about 3 times bigger than the legacy Flash game).
More collectibles and weapons in which the efficiency and power grow roughly quadratic.
New bosses and enemies.
Semi-endless game - No true endings, but fake endings are worth a great prestige or a rebirth.
Vastly rescaled player stats, from the start to the end.
New music (non-original soundtrack borrowed from the "Copyright Free Music" common songs and instrumentals, extended versions of the old songs).
Experimental development version 1 - "The Great Update"
Experimental development version 2 - "The Great Tweaks"
Experimental development version 3 - "Mastery Update"
Location Danger Index (LDI) - Numeral-based location danger scale