Keith,
Actually, the low placement of the headlight on an articulated is done for a very sound reason.
It is not access, it is because the lead truck is first into a curve. When the headlight is mounted there the Engineer can see where he is going much easier than having to rely on a boiler mounted headlight that will follow the rear truck and be shining off into space as you round a curve. Vision as far ahead as possible is particularly important if you are following a river, operating on a track which is particularly prone to rock slides or occupancy by errant wildlife.
Yes, there were some headlights mounted on the boiler front, but in talking to the men who actually operated these machines in daily service, the headlight mounted on the front engine was preferred over the boiler mount. UP had the boiler mount on their CSA class (the little Challengers) but when the Jabelman designed 4-6-6-4' and 4-8-8-4's came along the headlights were mounted on the leading engine, above the pilot.
These Headlights look low, but are still about 7-8' above the ground. You have to climb up to replace a headlight bulb.
Rick