There are some possibilities here but having flash based causes some restrictions.

I would have a day and night mode set up for voice mail/aa. During day they would get the day menu on the voicemail and restrict any transfers to only the operator. Actually it should ring to the operator instead of AA. In essence, it is going here anyway after the AA gets the call. Set all digits on vm to transfer to office if it RNA.

During a night greeting, program a second menu that allows direct extension transfers. Put in forwarding for RNA/BUSY.

You can also set up an auto day/night timer in the phone system to change with the times you provide. You can use the operator station DND as an override if needed for special function days.

There are things that can be done but it really needs to be defined. They also need to know limitations on how calls are processed once it's programmed. Best would be to draw a flowchart of call progress.

Tip and ring, the work of the devil!