Below is a list of the things that are missing from C2 event system, this could be considered as a suggestion list for C3.
-Duration and Countdown Timers as conditions: Having a condition "After X seconds" (Countdown Timer - runs constantly after specified time) or "For X seconds" (Duration Timer - runs while the timer is below the specified number of seconds, after that it stops executing) would make things a lot more easier. These two will stop counting if the parent is no longer active (in contract with the "wait" command).
-"Replace" command (key R) doesn't work for all behaviors, mainly "Pin".
-"Is changed", "Is incrementing" and "Is decrementing" are three conditions that are time-savers for a lot of things. Would be cool to have them. They check the change of a specified variable / tick elapsed. They only run once per activation (meaning if a number is incremented 4 times in 4 ticks, they will run 4 times - can't run more than once per tick).
-Audio time markers. Setting them on music tracks and calling events when the marker is played (useful for precise audio timing)
Let me know what you think or if you want to add something.
EDIT: Also forgot about vectors variables. It would easier and faster to have vector variables to store values instead of defining X and Y separately. Some vector functions would be cool too, like random cone, random circle, normal, etc.