In my opinion, having logic gates such as such as AND, OR, XOR, NAND would be most important.
? AND, OR, and XOR are already part of the arithmetic combinator, you just have to normalize all true to 1 and all false to zero first (which is easy if the inputs are coming from decider combinators ...

My vote/opinions with full nuance:

Anything that creates new bootstrap complexity should be avoid in regular mode of play. (Hard or custom setting are okay).

Reasonable power draw is fine for all entities otherwise.

From a player's perspective, a belt an entity, not a single square segment of ...

I'd say making the aliens intelligent is a no-go. The genocide of native Americans is a pretty standard sci-fi metaphor, so that would make the choice seem to be "Genocide Yes/No?", which would make the current main mode of play something many people wouldn't consider choosing.

As other people have ...

Clock combinator
A timing and counting combinator to more simply implement time based logic.


What ?
A combinator with three modes. All three modes accept a duration parameter (measured in ticks) with a minimum value of one.

Delay mode
input is relayed, unaltered, after a delay of x ticks ...