An ASA's remote access SSL VPN needs to be bound to an interface address.
However while it uses SSL, it does not need to be on tcp/443. You can switch it over to some other port number like 8443.
There's an official Cisco technote covering this (bit dated - it still refers to WebVPN - but still valid) here:
http://www.cisco.com/c/en/us/support/docs/security/adaptive-security-device-manager/118842-technote-asdm-00.html#anc10