[plt-scheme] Literate scribbling question

I was experimenting with the scribble/lp language, and found the need
for the @chunks rather frustrating as they take up horizontal space
and introduce a required chunk label. Replacing the @chunk calls with
@schemeblock made the resulting scribble document (generated via
lp-include) look very nice, but the source file was no longer a valid
PLT Scheme program (in the sense that, when run, it would yield an
error due to not having any chunks).

At this point I realized that what I actually wanted was quite close
to scribble/lp, but not quite the way I understand it to currently be.
I'd like the labels to just come from define forms (perhaps with the
option of me labeling other chunks for inclusion in the table of
contents), and I'd also prefer to not have to annotate a valid
syntactic form at all. This latter is perhaps unworkable, hence this
email: Could we switch the reader into Scheme mode when encountering
an un-escaped left-parenthesis, and remain in text mode at all other
times?

Has anyone with more experience at custom languages and readers in PLT
already done this?

Anthony