Partial read-only (according to syntax)

[komka_peter_3x]

It would be very nice feature if in a "read-only" file, certain parts be yet editable. And the syntax highlighting would recognize/show that.
E.g. there is a source code, with some special "comments":

xxxxxxx xxxxxxx xxxxxx
xxxxxxx xxxxxxx xxxxxx
xxxxxxx xxxxxxx xxxxxx
/*-editable-part-begin-*/
/*-editable-part-end-*/
xxxxxxx xxxxxxx xxxxxx
xxxxxxx xxxxxxx xxxxxx
xxxxxxx xxxxxxx xxxxxx

Between that lines, the user could insert and edit text. But the remaining is read-only. The colors: all the text is e.g. light blue, except that inserted parts (where follow e.g. the C++ syntax's red, green etc.).