Conforming DOM subset in <data/>

Just a short question this time: 
 
Can implementation be conformant with VoiceXML 2.0 specification if the
DOM exposed by <data/> is read-write ? And if not please explaing why
(and i don' t mean why in context: cause there reads "as real-only
subset" in latest candidate)? And did you evaluate the possibility to
use E4X ( ECMA-357 ) instead of W3C DOM (If I remember correctly there
was some discussion about this..); the E4X interface IS more ECMA
oriented than DOM mapping.. And please be more prompt what is the subset
for dom. createElement is hardly readonly method. What you mean by
read-only; that the user is not able to create new documents ?
 
- Teemu