Mirakels had a very good idea: Instead of patching obexd to use "the old" signalling about PC Suite mode it would be better to make the N900 understand "the new" signalling from obexd upstream version.
Therefore /usr/sbin/pcsuite-enable.sh could get an additional entry and maybe /usr/sbin/pcsuite-disable.sh
For /usr/sbin/pcsuite-enable.sh I think an the entry should be below line 61: kill -USR1 $OBEXD_PID
and it could be:
dbus-send --system --type=signal / com.meego.usb_moded.sig_usb_state_ind string:'ovi_suite'

With this line added - in theory - both obexd versions should work with PC Suite. I did a test from commandline and there was a log entry from obexd, that it received the signal.

Maybe it is necessary to add the following line to /usr/sbin/pcsuite-disable.sh
dbus-send --system --type=signal / com.meego.usb_moded.sig_usb_state_ind string:'USB disconnected'
But I don't know whether this is true.