If you have available SL and LS ports here's a cool trick to get you there:
Loop one or more LS ports to the SL ports. Put the LS in a TG. Flag SLs to be HOUSE PHONES and dial 8 when they go off-hook, and be sure ASSOCIATED EXTENSION for outside calls is ARS, also require ACCT CODE for LD calls. Block international for all phones except the SL ports. Now here's what happens: user dials access code for TG above. This becomes a new call on SL port, which automatically dials 8 for outside (looks to PBX like an analog phone went off-hook). User dials ext for the new TG, now hears dial tone from the SL port. User dials international number and the call is processed as if it's an analog station making it. Should beep for acct code (won't see display because it's analog). Haven't tried it yet, let me know if you have problems and I'll think about it more.
To make life easy you might want to change feature code 5 or 6 to something else, then use that single digit as the TG ext so it's one-digit to get there.