Well, obviously the final game will have multiple multiballs, not just 1.
Once you clear the 4 villains currently, it just restarts, there will be something there later.
All the sub villains don't do anything currently.
The game barely has any call outs.
Apparently there are 1400 video clips in the rom, we barely see any of them.
So, software wise there is a long way to go.