What I had in mind was a slightly higher level
system view.

So starting at the easy end, we might specify that
the AF amp takes 100mW into 600 Ohms, and
delivers 1W out into 8 Ohms. a biscuit to do that
might take many forms but would all be interchangeable.

If an audio filter were to be included, that would
work in and out at 100mV into 600 Ohms with
0dB gain - and would thus be an optional fit
prior to the AF amp.

I'm not thinking in terms of mother and daughter boards,
but of a set of standard biscuit designs that could then
be assembled into whatever, test eqpt or rig.

Although we'd be using small miniature components (is
anything else readily available these days?) that miniaturisation
does not have to feature in our biscuits necessarily, so
we might have SMDs but spaced out by half-an-inch, or so,
to enable us to work with them.

Setting aside the infantile remarks and attention-seeking
from "the usual suspects", I'm proposing that this be a joint
effort.
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Just for information :
A modular approach to homebrewing (call it biscuit building) is also
very well propagated in the book : Experimental Methods in RF Design ,by
W7ZOI , KK7B and W7PUA. Most modules are built in 'ugly contruction'
style for best possible (RF) stability and low cost .

Frank GM0CSZ / KN6WH