ESS/MSS outside Firewall

Hi

I have a requirement to expose ESS/MSS outside firewall. From my research looks like, external facing portal may not work for heavy webdynpro applications like ESS/MSS. Is it true with 7.3 portal? if so is there any other way to make ESS/MSS to accessed over internet?. FYI, portal would be 7.3 and ESS/MSS would EhP6 WDA.

Thanks, Raj