Yakov,
If the need for the loop back address is to establish a router ID then, the management interface could be used for the same purpose or a sub-interface.
You are right, loop back interface is not supported on the ASA. If you have an account team that you work with, I suggest that you reach out to them and see what they could do regarding this request.
-Kureli
Checkout my breakout session at Cisco Live 2013, Orlando, Florida.
BRKSEC-2024 Deploying Next-Generation Firewall Services on the ASA
Room 314A Tuesday, June 25 3:00 PM - 4:30 PM
