Grateful Dead songs are inherently tricky to translate from recording to notation and especially tricky to translate back into action, so that's why. Also, there might be a lot of tabs out there but not too many good GP files which most people use as their starting point for customs. I have two song books and I still wanna release a few more GD customs but it takes way more time and work than other songs, so I usually put it off. :)
There's no real way to pan tones in RS, so that's why the Toolkit doesn't support it. The only way to get stereo imaging is by using a stereo rack effect like the Stereo Chorus. I use that a lot for spreading tones left and right to get it away from centre position and make it integrate more with the track, especially when the instrument is panned to the side.