Dutch ovens are necessarily really heavy aren't they? To spread the heat uniformly. Though there's a "camping" one at that wiki link, I wouldn't fancy backpacking it. The aluminium one they mention would be light
er, but still not very light (for same reason).
I'm not sure about alum foil, but sounds worth a try. the melting point is high enough, but so thin... There's a (NZ) maori tradition of roasting by wrapping meat/veg in leaves (foil would do), then burying in coal and heated stones. Might work for bread, too?
If the idea of an oven is uniform heat (idk, is it? IANAC), that buried in coals & stones seems pretty good, with foil to keep ash out. If hot air is part of an oven (again, idk), maybe a little space at the top could constructed too.
When I've attempted damper, I've lost a lot, in the form of charred skin. Maybe I'm doing it wrong.