"If I understand, your program assigns for each key a finger and then, based on the computed position of this finger on the guitar, the bank / preset is automatically chosen?"
The program does assign a "patch" and a "note" to each string/fret location on the fretboard. The patch is user-selectable for each string. So, strings 1 thru 3 could be assigned a "bare finger" patch for a given guitar type (classical, acoustic...). And, strings 4 thru 6 could be assigned a "playing with a pick" patch that was also "palm muted" when sampled. This would be the standard, Travis Picking way to "voice" these strings.
And, the user CAN assign a finger to a string/fret position on the fretboard. This is one way to "search" for a specific chord in the database and is also used to "create" a new chord or "modify" an existing guitar chord. Of course, chords can quickly be searched by chord name, as well.