Hi Madsen,
ABAP code to identify what endian type the current server is using
This you can easily also write yourself, something like
FIELD-SYMBOLS <x> TYPE x.
ASSIGN '1' TO <x> CASTING.
IF <x> = '3100'.
...
ELSEIF <x> = '0031'.
...
ENDIF.
currently looking af CL_ABAP_DOCU_SERVICE_METHODS method CONVERT_TO_UNICODE
Wanna pull my leg 
. No, no, no, You don't use CL_ABAP_DOCU_SERVICE_METHODS. Accidentally that's my class and its documentation clearly says "Only for use in the package SABAPDOCU". (SABAPDOCU is encapsulated and CL_ABAP_DOCU_SERVICE_METHODS is not published in a package interface). And it doesn't do what you intend at all ... (b.t.w., the official class for converting from and to codepages is CL_ABAP_CODEPAGE).
But why not take a look at
EXPORT|IMPORT ... TO|FROM DATA BUFFER?
That's the easiest way how to "serialize" ABAP data to byte strings!
(The more sophisticated way is an XML serialization but this is for data exchange while you are talking about data storage).
Horst