It would be very useful if the slicing mechanism was available for use with non-repeating (cardinality 0..1 or 1..1) elements in order to define choice(s) of constraints.  These constraints could include different (multiple) value set binding (but of course would not be limited to that and would allow increasing cardinality restrictions or any other applicable constraints).  It should be noted that a non-repeating (max cardinality = 1) element is simply the degenerate case of a repeating element with only a single repeat - so the existing slicing machinery should already be applicable, if the restriction(s) that currently prohibit its use in this context were removed.

Apparently that the only place in the current specification where this is explicitly discussed and prohibited is in ElementDefinition.slicing here where it states that "Slicing can be used in any resource that has cardinality .. on the base resource, or any resource with a choice of types".  There does not appear to be a specific technical reason why this restriction is required.

[It is noted that there is discussion and plans underway for providing the capability for multiple value set bindings on an element - and this is one way that could be accomplished largely using currently existing machinery.] 

Slicing on 0..1 elements is currently being used in the published IPS IG, but with the more recent IG Publisher versions there are some remaining validation issues in the examples.  

See the Zulip discussion on [Slicing non-repeating elements to define a choice](https://chat.fhir.org/#narrow/stream/179166-implementers/topic/Slicing.20non-repeating.20elements.20to.20define.20a.20choice).