This is a wonderful surprise.
I wonder if Keys (Peter Coyote) is a co-IC or an "extrapolation character"--for a change mc, "this could be you in the future if you continue on your current path." I thought of this especially when ET is captured (this might be a handoff?) and Keys basically says, "I started as you. Keep pursuing and you'll be stuck in that phase of arrested development like me." Keys clearly represents another path, but it seems more like the polar opposite of ET with Elliott in the middle of that dilemma. A stark contrast to the steadfast character--even more so than the change character. Perhaps Keys is more of an mc handoff in that scene than an ic.