Use "dpkg-deb -x" to extract the contents to a temporary working directory. Use "dpkg-deb --control" to yank out the debian/control files to the temp dir. Modify your control file with your favourite editor and then repackage the entire directory using "dpkg -b".
Nokia-N900:/var/tmp# dpkg-deb -x /home/user/MyDocs/wl1251-maemo/binary/osso-wlan/osso-wlan_3.0.20+0m5-1_armel.deb /var/tmp/remod2/
Nokia-N900:/var/tmp# dpkg-deb --control /home/user/MyDocs/wl1251-maemo/binary/osso-wlan/osso-wlan_3.0.20+0m5-1_armel.deb /var/tmp/remod2/DEBIAN/
Nokia-N900:/var/tmp/remod2# dpkg -b /var/tmp/remod2/ /var/tmp/remod2/osso-wlan_3.0.20+0m5_armel.deb dpkg-deb: building package `osso-wlan' in `/var/tmp/remod2/osso-wlan_3.0.20+0m5_armel.deb'. tar: unrecognized option `--format=gnu' BusyBox v1.10.2 (Debian 3:1.10.2.legal-1osso30+0m5) multi-call binary Usage: tar -[czxtvO] [-X FILE] [-f TARFILE] [-C DIR] [FILE(s)]... dpkg-deb: subprocess tar -cf returned error exit status 1