I'm feeling pretty good about this :)

jakob@Epsilon ~/Code/guix [env] $ sudo -E ./pre-inst-env guix system reconfigure ~/.config/guix/system/config.scm 
substitute: updating substitutes from 'https://ci.guix.gnu.org'... 100.0%
The following derivation will be built:
   /gnu/store/327py2dv6xjlm0xanqiqj1paxxx8g1rq-grub.cfg.drv
building /gnu/store/327py2dv6xjlm0xanqiqj1paxxx8g1rq-grub.cfg.drv...
/gnu/store/h45l455dg3wi6b24m0v8as5wdjskpfsm-system
/gnu/store/razfpshw9n33dvm4bp0d2jwpdf4255hf-grub.cfg

activating system...
making '/gnu/store/h45l455dg3wi6b24m0v8as5wdjskpfsm-system' the current system...
setting up setuid programs in '/run/setuid-programs'...
populating /etc from /gnu/store/glzrd1cb6ngzwqvnph3q3pbxxjv8nprs-etc...
substitute: updating substitutes from 'https://ci.guix.gnu.org'... 100.0%
building /gnu/store/8vn3dlcmhri0f3ygfhqavlab2q35q2yn-install-bootloader.scm.drv...
guix system: bootloader successfully installed on '/dev/sda'
substitute: updating substitutes from 'https://ci.guix.gnu.org'... 100.0%
building /gnu/store/43cyy0nnrdr6wg9xzcph6shs4w7gfxi6-upgrade-shepherd-services.scm.drv...
shepherd: Evaluating user expression (let* ((services (map primitive-load (?))) # ?) ?).

Jakob L. Kreuze (3):
  guix system: Add 'reconfigure' module.
  guix system: Reimplement 'reconfigure'.
  tests: Add reconfigure system test.

 Makefile.am                         |   1 +
 gnu/local.mk                        |   1 +
 gnu/machine/ssh.scm                 | 189 ++------------------
 gnu/services/herd.scm               |   6 +
 gnu/tests/reconfigure.scm           | 262 ++++++++++++++++++++++++++++
 guix/scripts/system.scm             | 186 +++++---------------
 guix/scripts/system/reconfigure.scm | 237 +++++++++++++++++++++++++
 tests/services.scm                  |   4 -
 8 files changed, 560 insertions(+), 326 deletions(-)
 create mode 100644 gnu/tests/reconfigure.scm
 create mode 100644 guix/scripts/system/reconfigure.scm

-- 
2.22.0