These two new properties will, unlike other DFDL properties, need to have a default value if they aren't defined.

bitOrder='mostSignificantBitFirst'
encodingErrorPolicy='replace'

should be the defaults.

There should be a separate Daffodil-specific switch that turns on/off whether these properties get default values or not. E.g.,

daffodil:features="bitOrderRequired encodingErrorPolicyRequired"

The flag, if present, would disable the default.