Exchange access over the net with a prox

I have a boss that wants to open up the exchange server for home access. Not OWA and not Pop3 but normal access. My exchange server is behind a MS proxy 2.0 server. Is this possible and how would one do it? What are the risk’s involved with it. We have OWA running now on the 5.5 box but most people have laptops and are on the road alot.