An attacker can hack the program running the server and any program/service it relies on e.g. SSL, the webserver, logins etc.). No system connected to a network and plugged in is unhackable. If they can successfully exploit your Pi, they can then use it to attack your other servers - this will likely be far easier since they already accessed your network and there is likely a degree of trust between your Pi and other machines on your network. You need far more than port forwarding to protect your Pi and the rest of your network. This would include but is not limited to a firewall, intrusion detection, an update/patching plan, backups hardening of all exposed services and programs etc. 

I would suggest doing much more homework before attempting this or trying to convince your boss - unless you want to be unemployed. You may want to start with this [question][1], and this recent blog [post][2].


  [1]: http://raspberrypi.stackexchange.com/questions/1247/what-should-be-done-to-secure-raspberry-pi/1250#1250
  [2]: https://www.inversoft.com/guides/2016-guide-to-user-data-security