|If it were me, I'd be looking into VPN solutions.|
Preferably a VPN solution that allows one to create VPN groups as well as users. This would make controlling/restricting access a little easier I would think.
Granular control over who gets access to what is important when you're allowing external, non-employees access to internal resources.
It matters not how straight the gate,
How charged with punishments the scroll,
I am the master of my fate;
I am the captain of my soul.