Currently, properties of complex types are individually selected, as in:
$select=Name,Address/City,Address/State,Address/Zip

We could simplify the syntax for selecting individual properties of a complex type, similar to expand options. Something like:
$select=Name, Address($select=City,State,Zip)
or
$select=Name, Address(City,State,Zip)

The first syntax would support adding the ability, for example, to $filter or $sort a collection of complex types.

We could put $compute (or an inline expression) in the $select in as a scoped value (couldn't be used in filter/sort).

Putting $expand in $select brings in all the issues of combining $expand and $select and results in two ways of doing expand.