Easy off/on layer ing fo rthe lower half?

I carry windpants(Montane) that have zips long enough to allow pulling em on over shoes.

It's amazing how much warmth you can get by pulling windpants over hiking pants.

Windpants are light and have many other uses as well.

I also carry a sit pad so that I can sit on cold and/or wet rocks for breaks.

There are pants that are designed for skiing that have lower zips to accommodate ski boots. I don't know if any are UL though.

200 weight fleece under waterproof or wind pants would be good for cold and wet conditions.

OtterLegs:
http://www.ottertrek.com/Products.html

Polypro leggings (light, warm for weight, and water resistant/fast drying)? Like these: http://www.amazon.com/Pace-PolyPro-Cycling-Warmer-Medium/dp/B001AX6T74/ref=sr_1_1?s=apparel&ie=UTF8&qid=1379597346&sr=1-1&keywords=Pace+P3%2B+PolyPro+Cycling+Leg+Warmer

Plus rain kilt that one can easily put on over the outside.

I've always found long johns and shorts to be a good starting point, then windpants over if it cools off. You'll want side zips (at least partial) to get over those 15EEE's. Depending on the weather you can vary the weight of the long johns, although personally I find that just lightweight longs and windpants are good for me down into the 20's on the move, except for when it is really cold and wet – 40 degree rain calls for the expedition weight bottoms with wind pants over.

Another way to go, if you like zipoff hiking pants, is to wear long johns under them. The its' just a matter of zipping on and off the lower legs for adjustment. I have some REI Sahara zipoffs that I use for work which have lower legs that separate so you can get them off without removing shoes, or even snowshoes or skis.

Also see the recent article here on tights.

get full zip rain pants … and put them on top when you get cold

;)