Very interesting. And epic post indeed! Seriously considering the springs and isolators. Quick question though. Could you combine both a BB and spring/isolator replacement and what kind of results have you experienced or heard about this? Sorry if it's been answered already in your thread. Army has me working stupid hours so I'm getting kind of lazy.....
Sorry, for some reason my JF notifications weren't getting emailed over so I didn't get your question till today.
My final configuration with the 2" lift was to add the 2" springs, Bilstein shocks, new spring isolators all around, and 3/4" spacers up front. In the suspension, I added longer sway bar end links in the rear, Rough Country disconnects up front, and a JKS track bar and JKS tie rod. The 3/4" spacers made the WJ look more level (the rear fender flares are higher than the front). It also gave a little more height which is lost when I have my winch on the front (it's a multi-mount, can remove it when I want to).
You technically CAN mount 2" spacers on top of 2" springs but its not a very good idea. It's not as simple as just putting in the spacers and springs and calling it good. WJ lifts start getting more complex and expensive at 4". You need longer shocks, longer front control arms, rear a-arm spacer or new a-arm, longer sway bar end links front/rear, longer/adjustable track bar, driveshaft (on some WJs). If you really want a 4" lift, then sell/return your spacers and buy a mostly-complete kit which has most everything you need at a better price than piecing it together. A very popular 4" lift is the Zone Offroad kit, starts at $700, and has a lot of good reviews for ride/install. The cheaper kits are less complete and lower quality, in my opinion, good 4" lifts start around $700 and GREAT ones are $1000+.
Hope this helps.