Would a CPL be the best solution to mimic Nikon's D-Lighting on a Canon?

The ALO and HTP don't seem to make a difference in my Canon T1i. I just want to know if it would be a good idea to get a CPL filter. Also, if it wouldn't be a problem to mount both CPL and UV on the lens.

Another question, would a CPL only be most useful on a wide-angle lens? I have a 50mm and a long telephoto too and was wondering if I should get a step-up ring for it.

A CPL won't increase your dynamic range which is what D-Lighting is supposed to do, it mainly decreases reflected light, when used properly. While you can mount both the CPL and UV filters, I would only mount one or the other just to minimize the amount of glass.

Because the wide angle is looking at more things and could be exposed to more reflections, it might be more useful. If you can get an adapter for your other lenses that is cheaper than another CPL, go for it.