As a harp has diatonic pitches strings, and pedals for # and b,
The diatonics notes would be the white keys,
and 7 pedals would be assigned to the 7 groups of 3 middle black keys, as it,
from left to right of a 7 octave MIDI keyboard :

RE   DO   SI    MI   FA   SOL   LA
D    C     B      E     F    G       H
... .. ... .. ... .. ... .. ... .. ... .. ...
so that, for example with the D note,
the MIDI Fa# key would set all the D to D#
the MIDI Sol# key would set all the D to D becarre
the MIDI La# key would set all the D to D bemol

this for the 3 notes D, D, B.
But the inverse, for the 4 other notes, so that a harp player could visualise the MIDI keyboard as the 7 pedals down of the harp, with their movements made by foots.

Then, it would have the need of modelising the place of note articulation in the string :
in the middle, or down the string.
Muted sounds (with hand) would be made by Velocity between 1 and 5 and no volume, to stop the string.

Or by pressing the sustain pedal, with the notes we want to stop, still pressed on the keyboard.

For Harmonic sounds, well, how...
Assume that if the Do# key of the MIDI keyboard is pressed in the same time as a white note, this white note is an harmonic sound.
And the velocity of the Do# determines the place the harmonic is played :
64 = middle of the string
127 = 1/4 top of string
0 = down the string

  Note if far of the middle of the string, the real sound is a "missing" sound, that would be insterresting to modelise !

  it would be so interesting to modelise what happens when to low pitch stings enters each other in toutch : "frisements" in french.

  it would be so interesting to modelise what happens when a pitch pedal changing (b - Becarre - #) by playing the string : a special square pitch bend effect, but not only : the mechanic Herard system "plays" the string at it end by the changing.
  So Pedal velocity could be modelised, so that even if no MIDI keyboard pressed, we could hear the Herard pedal mechanics "playing" the notes by changing their tonalities.

  so if "pedal keys" "played" gently, near nothing happens. But if "played" strongly, we can hear the sound what harpists wants to hide by playing harp. But more realistic modelising !

  The first bass octave string ( -> SOL / G ) are metallic, and the other are made in "boyeau de mouton" or nylon (less good sound)

  There are only 3 types of harp sounds on VSTi :
.in the tiny General Midi banks (basics samples )
.one in Garritan Orchestra (some basic samples a little better, but less usable as The Grand for the piano...)
.one in Reality preset banks (good musical samples, with bass strings, but Reality is today unusable because left by programmers)

.i don't count the joke "Harptime" but it was a good joke, to modelise a tiny FM quality harp sound.

  So the harp is often used in a huge amount of musics and even contemporany music.
So, after Pianoteq, if Harpteq would be there, i buy it.