i pretty much always have wool projects going ---i love working with wool!
when you disassemble your clothing and wash it---wash it in hot water- with detergent- a regular cycle===rinse in cold water =then dry in a hot dryer---it will not ravel when you work with it- and you will not need an interfacing----i've made very large wool quilts and have never (lined) a single piece of wool- and have never had one ravel or fray.
i do not understand how you can get more usable wool from a pair of pants then from a jacket- since with a jacket you get a very very large piece from the back---and the sleeves are generally wider than pant legs===i use both but have always thought the jackets were by far the better deal...i will have to (study this) a bit...i'm attaching a picture of one of my wool quilts---also starting a new thread with some of my (in the works) wool blocks for everyone to see
once i started working with wool i was HOOKED! it is my favorite fabric!