as time allows, I'm going to post a video or sound snippet of the technique I suggested... but in messing around preparing for the video, it occurred to me that most of what I was doing with the harmony pedal was scale based... so any harmony creating device should work.

From a recording standpoint, you should be able to play single note slide guitar into Real Band, then apply the TC Helicon harmonizer to it and get something pretty close to what I'm talking about.

If you added harmony to a copy of the single note track, you could use volume envelopes to switch seamlessly between the tracks for parts where you don't need a full chord.

in fact, you could also use volume envelopes to substitute for the volume pedal used by pedal steel players to fade in the sound.

BTW, I like to add a 3rd and 5th to the single note in order to get the full chord sound so often played on steel guitars.

https://www.dropbox.com/sh/ey71h8ep047758h/AAC12jNM0Hz9Q8zsh5iDeqNHa?dl=0