No the utility I'm talking about will only "compile" input xml-files once.
It wouldn't increase performance, but it would simplify the code a lot
Basically you write an XML file, and before you use it - you pass it through
the preprocessor/compiler/whatever to generate a valid EQ2 ui xml.
It would automatically use the EQ2Ext lib.
However, it's also possible to try simplifying EQ2Ext as much as possible,
giving lots of sample code for reference.