Extended brake lines aren't necessary, but in my opinion are nice to have for the $$$. Plenty of people still using stock brake hose and flexing just fine.

Lift amount doesn't matter if your are planning on flexing the front end. All a front suspension lift does is change the static vehicle height. If you offroad much you will still cycle the front suspension through the original front suspension arc. You will need to do some trimming/clearancing to allow the full range of motion with 285's or anything bigger than stock. If you're a mall crawler then you may have to deal with a little rubbing without trimming.

Panhard correction kit would help with handling at lifted heights.

It looks like both front and rear shocks come with all the needed bushings/washers but I would email wheeler's customer support to verify.