BLknotes,
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The dupletes, bends, slides, & vibrato of guitar require the use of two hands. One to play the guitar(right hand) and the other to use the joystick (to far left of keyborad) to obtain the effects.

It's possible to do it on G-70, let's say as the Roland vocabulary, G-70 has 3 "right hands" and 2 "left hands" + Intelligent arrangement (related to right hand analysis). Each note can have different sounds and effects related to the velocity and aftertouch. If you press the note deeply, the sound can trig to another sound and the effect too.

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Maybe a foot switch.

You can do it with FC7 foot/switch controler (7 programmable switches).
I don't know if you have the opportinuty to play on an Organ "Atelier" or Yamaha "Electone". You can do the things that we never believe.