is the cp1 really metal? i know the lamy st, which is all metal, and also a little less expensive. i own the lamy st tripen and the lead isn't springy like it is in the scribble. and about the mechanism, i bet lamy uses Schmidt systems, as almost every german company.

here are few metal (not always solid) mechanical pencils with sleek straight aesthetic i know:

Staedtler Organizer is very thin and designed to be used with notebooks.

Faber Castell Ambition Black resin with metal. Twist lead advance system.

Faber Castell Basic with a rubber grip. there is also a shiny version of it.

Lamy 2000 has a 100% metal version too, but its a very different price caterogy.

Since you mentioned the kaweco sport al (a pocket pen), maybe you could look at the Kaweco Special as well. there is a black anodized version as well. both aluminum.

The rOtring 800 is the one with retractable sleeve? I know one of the rOtrings very famous pens have a fixed very very thin sleeve, that could bend once it falls. It is surely a nice drafting tool, but probably meant to be kept on the desk of an office. A bent tip would be a headache...