Hello Vash,
Yes this is possible.
Its not exactly NAT as you are thinking but check the following:
ip multicast helper-map
Usage Guidelines
When a multicast-capable internetwork is between two broadcast-only internetworks, you can convert broadcast traffic to multicast at the first hop router, and convert it back to broadcast at the last hop router before delivering the packets to the broadcast clients. However, broadcast packets with the IP source address of 0.0.0.0 (such as a Dynamic Host Configuration Protocol [DHCP] request) will not be translated to any multicast group.
Thus, you can take advantage of the multicast capability of the intermediate multicast internetwork. This feature prevents unnecessary replication at the intermediate routers and allows multicast fast switching in the multicast internetwork.
If you need to send a directed broadcast to the subnet, the outgoing interface of the last hop router can be configured with an IP broadcast address of x.x.x.255, where x.x.x.0 is the subnet that you are trying to reach; otherwise the packet will be converted to 255.255.255.255.
http://www.cisco.com/univercd/cc/td/doc/product/software/ios124/124cr/himc_r/mlt_i1h.htm#wp1075964
HTH,
vlad
