There seems to be a number of things to this game that needs some fixing.. and it may be worthwhile to do..
1) Add unused dialog to proper parts of the game. There is some dialog that you would think would be shown, but never shown because the game was most likely unfinished.
2) Fix the duplication bug (use FF4ET as a base).
3) Allow FF2US to use the FF4 Active option.
4) Add back in dummied weapons... perhaps adding a new script to trigger them.. like a script to check if all the vehicles surround Mysidia or Baron that some guy gives you the Assassin Knife... or adding the Hand Axe to a shop the town of Silveria/Mythril or to Cid's daughter as a gift or something.
5) Fix the Adamant Armor bug.

6) Apply fix for Stop status in FF2 v1.0 that was applied to FF2 v1.1.
7) Readd all dummied commands...?
8) Fix one dummied command not ever enabled in FF4.
9) Fix back row bit bug.
A more radical hack though is modifying the battle system to take advantage of the other defensive stats (evade and magic evade)... which would make for battles where Cecil can actually miss...
Another radical hack would perhaps add something like FF4A's character switching system, since in theory it should work the same way... not required but a cool idea perhaps.
Thoughts, other ideas, and random objections?