source code question about language check in LyX documents

[Uwe Stöhr]

Can anybody help me with this issue?:

Special lines should to be added to the preamble whenever e.g. Arabic is used 
in the document.
I know how to do this in Bufferparams.cp when Arabic is the document language:
if (language->lang() == "arabic_arabtex") {
        os << "\\usepackage{arabtex}\n";
        texrow.newline();
}

But \usepackage{arabtex} must be loaded whenever Arabic is used in a document, no matter if it is 
the document language or not. How can this be done?

thanks and regards
Uwe