The DNS approach you mentioned seems to be the most reasonable one. Others could be:
1) Use two different profiles
2) Perhaps use two different hostnames (and put the second as a Backup VPN gateway), based on where the user is currently on the network only one should be functional, but I'm not sure if this will even work...never tried it.
Table of ContentsIntroductionVersion HistoryPossible Future
UpdatesDocuments PurposeNAT Operation in ASA 8.3+ SectionsRule Types
Network Object NATTwice NAT / Manual NATRule Types used per SectionNAT
Types used with Twice NAT / Manual NAT and Network Obje...
Table of Contents Introduction:This document describes details on how
NAT-T works. Background: ESP encrypts all critical information,
encapsulating the entire inner TCP/UDP datagram within an ESP header.
ESP is an IP protocol in the same sense that TCP an...