X-

Much of what you ask is technically possible.  But there is a price to pay.

For some features such as wide aperture and wide zoom range, the price may
be weight and size.  For a compact lens, the price may be a limited zoom
range and small maximum aperture.

One particular 35mm compact camera I can think of has an f/2.8 lens, but
also has a 35mm fixed focal length.  In that case, 35/2.8 = 12.5mm or 1/2
inch maximum lens element diameter.

For a retractable lens, there may be a problem of reliability due to
mechanical complexity.  Of course that is not so much of a problem with a
point-and-shoot camera that would be cheaper to replace than repair.  When
it wears out after a year of use, it is obsolete anyway!

(I think Leica made a collapsible lens, but was fixed-focal length and
very precisely manufactured.)

Fred

who say there's no retractable zoom inSLR? They mostly ARE retractable. They
are just bigger. plain physics.

Not sure what you are talking about.  In some cases, lenses made
specifically for DSLR cameras are pretty small.  Most lenses do get bigger
and heavier when you increase the size of the aperture, and most
manufacturers best lenses are made for both full frame and DSLR, so they are
just bigger.

The only true retractable lenses I recall were made for rangefinder 35mm
cameras, and as you can tell most point and shoot lenses are retractable.
Too much stuff in the way to retract a quality lens on a DSLR.