I think it would be great if we had a conditional that simply checks if a set command can execute and make a change.
In some uses, This would just be a matter of convenience, In others, It would allow for entirely new conditions that wouldn't be possible otherwise.
Some examples include
CanExecute [Var [Health] = [Health:]] [True]
Var [Health] = [Health:]
// Player HP has changed since the last time this was executed.
// Would normally require 2 vars to be created in order to detect a change.
// Player HP has not changed since the last time this was executed."
CanExecute [CaveIn [x,y,z]] [True]
// No caveins active on the map, And the coordinates are valid.
// Determining whether or not a cavein is happening would normally require a conditional that doesn't exist."
CanExecute [CopyBlock [x,y,z] [x,y,z]] [True]
// Checks whether or not two blocks match each other exactly, Or of the coordinates are valid."
MC has this in the form of comparitors facing off of a command block, It effectively turns all commands into conditionals if you decide to use them that way, And I think it could be really useful to people who are more creative with scripts.
I don't know if scripts can tell whether or not the command actually changed anything, But I know that they can tell whether or not the command is valid, And if not, What went wrong. So it feels like this is half way there.