[XeTeX] TECkit mapping for Beta Code?

[BPJ]

Does anyone know if there exists a TECkit mapping for Beta Code?
<http://en.wikipedia.org/wiki/Beta_code>

I've found the betababel package, which I assume uses some single-
byte encoding, and am aware, though challenged to handle, that
some workaround to handle '\#=' as a text characters is needed;
any help in this regard would be much appreciated.

What I got are non-LaTeX plaintext files (which I'd like to not
need to retype manually at all) written with Greek in uppercase
Beta Code and Latin-script text (mostly English but some German
and French quotes) written in lowercase with Beta Code
conventions for uppercase letters and diacritics, plus the ad hoc
'**' for literal asterisks, moreover it uses 'v' and 'j' for
digamma and jod in reconstructed forms, and the non-Beta Code
conventions '_' for macron, and TeX-like '--' for dash.

I'm really suspecting that I'd be better off prefiltering the
sources with some ad hoc (computer) script before marking them
up, am I not?

/bpj