The easiest way around this is to set your inbound CO line group as DIL to your 3 member hunt group, then Delay that to the Auto Attendant group 47. Depending on what voicemail card you're using, you can then set the AA to route calls via Dynamic Routing to different places depending on the CO trunk ID The only issue might be the 4th caller is going to hear ring-back until the timers expire.

Sometimes the thoughts in my head get so bored, they go for a stroll through my mouth. This is rarely a good thing.