Using an external hard drive with file systems such as ext or xft on
multiple systems can be difficult when user privileges are scrambles
due to different user and group ids on different hosts. My best
current bet was to adapt the local user and group id of my user on the
machine I have root access to to the one on the machine where I only
have user access.

You can use usermod and groupmod to change the uid and gid
(http://www.cyberciti.biz/faq/howto-change-rename-user-name-id/) then

find / -user 1000 | xargs chown -h 2284
find / -group 1000 | xargs chown -h 2000

to change user and group ids of files accordingly (here, the initial
user was 1000.1000 and the final is 2284.2000).

Change all user ids on the external hard drive accordingly and it should work!