So by simply working for say, DHS you would be exempt?

nope,
by simply being a member of a organization duly authorized to obtain firearms , all members of that organization is exempt just the same as any LEO.

HRS134-11 (3) exemptions

     (3)  To regularly enrolled members of any organization duly authorized to purchase or receive the weapons from the United States or from the State; provided the members are either at, or going to or from, their places of assembly or target practice;


"organization duly authorized" would be the factor as what the AG determines that to be.
but in all accounts  a FFL is duly authorized.


the earlier example Joe clubs applies for a FFL and SOT , all members can shoot and insert mags over 10 rds in pistols and shot MG and SBRs. as civilians.