orderby enum should not contain complex types OR should project sub-properties that are not complex types

[baywet]

for GET /me/calendar/events we currently project an enum value of start and start desc.
This ends up failing on the service because the start property is a complex type and cannot be used for ordering.
The conversion library should either:

1. not project properties that are complex/entity types
2. project sub properties of the complex/entity types which are themselves scalar types (e.g. start/dateTime desc )

If we go with 2, this brings a couple of questions:

1. how many levels of depths should this support?
2. what's going to happen for consumers using that metadata to project enums / union types of constants which all of a sudden will see a / character appear, which is reserved in most programing languages?

This also impacts graph explorer as we're suggesting customers things that cannot work.