Stephen, IR illuminators are a little like invisible (to the human eye) spot lights. So you could certainly mount them at different locations, much like street lamps are mounted every X feet/meters.
How far away do you want to see - 50m, 100m, 500m?
Driveway has a line of sight of 120m from camera mounting point. Idea is to detect human at 100m+ and recognize features when closer.
Ok, that's beyond the range of any integrated IR camera I know of. The two IR illuminator approach will provide good quality images. My main question / concern would be how wide the cameras' FoV will be at 120m. Even with a lot of light, if the FoV is too wide, it will be very hard to make out even an outline of people.
I will often position the illuminator to illuminate an area that is closest to it, but have the camera covering that area located elsewhere. The effectiveness of illumination of a subject is dependent on the distance between the illuminator and the object of interest, not the distance between the subject and the camera.
For example if I was wanting to gather video of an outdoor yard and have two cameras mounted in opposite corners of the building I would aim the cameras crossing each other to get full coverage of the yard in the FOV. However the IR while mounted beside cameras would be aimed at the area closest to the IR. This also solves the issues of glare when the IR is trying to cover both areas near and far you point out, but it also solves the issue of glare from precipitation and also picking up glare from the other IR if that illuminator is in the FOV. This also has the benefit of requiring less power for the IR.
I hope I explained that properly.