This weekend I has a look at this issue and mostly got it working, but at the end failed on two issues:
1. `dpkg-source --build $path` allows absolute paths. The `.orig.tar` files must be placed in the directory from where `dpkg-source` is invoked from. 2. Most packages nowadays use debhelper, so `dh_builddeb` is used to invoke `dpkg-deb`. The former has the option `--destdir` but that one clashes with the same option being used by `dh_auto_install`, so it MUST NOT be passed through `$DH_OPTIONS`. 3. `dpkg-genbuildinfo` and `dpkg-genchanges` both have the option `-u` to specify a different directory for the build artifacts. 4. The last missing part is the hard-coded path for the `.changes` file: > 593 my $chg = "../$pva.changes"; `dpkg-buildpackage` has no option to change that. This is my summary for now as of May 2020. More details of my experiment at <https://pmhahn.github.io/debian-oot-build/>.
