NIS 2013: Building new system - installation sequencing?

I am going to be building 3 new Win7 systems in the next few weeks.

 

Ordinarily, in the build plan, NIS is installed more or less immediately after the O/S installed to minimize the vulnerability window.

 

Quite a bit later in the build plan, Firefox will be installed.

 

If NIS is installed first, then how will the NIS plug-ins/extensions which work with Firefox get installed?  The same may also be asked when I upgrade Win7 from the initial IE 8 to IE 10.

 

Thanks.