@Tim: That's a possibility, but I'm convinced its possible with XSLT alone (or at least for the major part), I'll keep an extention as a last resort.
@Ismail: I had already come across the nodeset functions, but they only work with markup tags, not pure text. However, your link (big thanks!) convinced me that it's possible to convert the string to markup tags with the use of some stringfunctions, so I'll try that now.
I really had expected there would be some standard function that would do this conversion automatically though!