I have a adjustable arm lamp with a magnifying lens that is portable. Another bench tool that sees a lot of use for atypical clamping jobs is a zyliss multivise, but I think your top is to thick for it maybe. Reading in the thread I started on tool trays has led me to consider adding some T-track to the edges for holding boxes and other bits and bobs.
Those ones linked above are interesting too. For now, I am using Grizzly track saw clamps (2 for $25 when I got them) and modified HF quick clamps. I removed the fixed end and bent and twisted the bar so it would anchor to the bench top. I also plan to use plastic workmate inserts instead of metal "dogs", at least initially.
I find that I use a doe's foot quite often. Mine is made of 1/4 inch white oak with sandpaper glued on the bottom. Mine is 3 inches wide, but I would probably make it wider now so that it is in holdfast reach of more dog holes.
I have two rows, spaced 7 inches apart. The front row is spaced at 3" and the back at 9". The back row is mostly used for holdfasts and one end of an oak planing stop that spans the two rows.
I may have gone overboard on such a small bench, but I have two rows of dog holes starting five inches from the end vice and every five inches for the full length of the bench. I think the rows are about eight inches apart. Most of this I never measured, just set a mark that had to clear one thing or another.