[Exim] Vacationing w/ same username

I have a system in which I don't allow telnet access to. I have set up a
directory called /etc/mail/vacation, which contains all the vacation files
for my users who request them (since I have their home directory set as
/nonexistent). I have set forward files up the same way, and have set the
option of check_local_user = false so that it doesn't check the owner of
the file. However, I have my vacationing set up the following way:

Under transports configuration:

vacation_pipe:
driver = autoreply
file = $home/.vacation.msg
file_expand
log = $home/.vacation.log
once = $home/.vacation.once
from = ${local_part}@???,
to = $sender_address
subject = "Re: $h_subject"

Under Directors:

vacation:
driver = localuser
require_files = $home/.vacation.msg
transport = vacation_pipe
unseen

My problem is, either exim or the vacation program is checking the UID of
the .vacation.once and .vacation.log and .vacation.msg files, and when it
finds that the UID doesn't match the ${local_part}, it fails. I need to
to not fail, because I, the sysop don't want to have to create home
directories for all these users, and would rather dump their vacation
files all in one basket.

Is this possible?

Sincerely,

Richard G. Duvall