No Yamaha new CP series in Tom Lee... sad..
Anyway, back to your topic.
Emulating a real guitar is near impossible with hardware. First, we need to understand a little about guitar playing.
There are:
1. Plucking: plucking in different positions along the fret produces different tones - ie closer or further from the bridge, how it's plucked, slides, hammer ons and pull-offs etc)
2. Strumming (there's up and down strumming, stopping the sound with your palm, and noises)
3. Other noises (fret noises, hitting the body like a conga etc).
Obviously, it's near impossible to produce all these. It's easier for playing finger plucking. But you need to remember that the guitar only has 6 strings (most guitars anyway) and the keyboardist has 10 fingers (or 8 fingers and 2 thumbs) + sustain pedal. We need to think the way the guitarist think when playing with a keyboard - ie only 6 sounds at any one time. I would force myself to use 6 fingers (3 left and 3 right) and try as much as possible not to use the sustain pedal - use fingers to hold the notes down.
Some hardware keyboards now has programmed in multiple articulations depending on how you play plucking - eg playing a note and holding it down while playing the next note will trigger a hammer-on.
For strumming, it's more difficult. To get up and down strumming the right way and realistically is near impossible.
The most realistic way is via softsamplers which lets you trigger multiple articulations. But even then, strumming is not easy, although we are coming close.
Best way - is not to try to emulate strumming the guitar. If you have one lead guitarist and need another guitarist to play strumming, you as the keyboardist can play keyboards - and shouldn't try to emulate guitar strumming if you can't get realistic sounds. There's no fixed methods, but some suggestions are:
1. Do not use guitar patches. Use keyboard patches with fast attacks - ie electro-mechanical sounds (piano, e-piano).
2. Play syncopated chords instead of straight timing.
3. Don't play the same chords in succession. Example: C chord. If you need to play C for four beats, you can play C - F/C - G/C - F/C - G/C - C etc syncopated. You can also use arpeggios (but emphasizing on syncopation).
4. Do not try to get into the way of the lead - ie do not use the same sonic space. You can play high or middle range depending on where the lead is playing.
5. Don't always use triads. Fast syncopated 6ths work just as well, although I prefer to use them in the higher rance (ie away from middle C).
6. Quick arpeggios up and down the keyboard can be used occasionally. E.g. for C - I often use Cmaj7 or Csus4. Play around with alternative chords.
7. It's hard to put it down in writing. Better seen and heard than explained...
