Multi-line, 1 directly to VM, no ring, other ring as normal

Auto Attendant is a reasonable way.

You could also:

• make a user extension and change the call handling to go to voicemail only but uses a license
• make a common area phone extension and have the call handling go to voicemail only but also uses a license                                                             
• use a call queue that has no agents, but no advantage over the Auto Attendant

What do you mean by "with two extensions"?

Personal extension and a "hot line" extension.

in the old call manager system, I had the "hotline" going directly to voicemail, used a CTIPort to setup a ghostphone that I could assign and extension to and not directly to enduser phone. 

End user doesn't want "hotline" ringing on personal extension, support on hotline is leave vm, will can back in 24hrs type of support.