Maybe not so much a question of having aircraft some of us will never get around to, as having some significant types present so there are fewer gaps in the ORBATs and more variety in the air. Some - the 2-seaters, say - could be AI-only to save build time.
Since the 'wish list' question's been asked here, here's what I'd like to see.
RFC/RAF
Sopwith Dolphin - a prominent type in 1918, much more so than the Snipe.
Martinsyde G.100 Elephant
...and some widely-used 2-seaters...
Airco D.H.9
Armstrong-Whitworth F.K.8
B.E.2e
Luftstreitkraft
Pfalz D.XII
LFG Roland D.VI
Pfalz D.III (relatively easy mod of the later D.IIIa)
Siemens-Schukert D.III
Albatros C.III
1917-18 general purpose 2-seater, eg LVG C.V and C.VI
Aviation Militaire
Morane Saulnier Type N (small numbers but sexy and served with RFC too)
Farman F.40 (widely used, by RFC and Belgian air force as well)
Voisin 3 or 5
Morale Parasol LA or P
Salmson 2
Dorand AR.1 or AR.2
Just for discussion, the aircraft type that have been chosen over the years for addition to WOFF were always "stalwarts" or workhorses that tended to cover long periods of time and could be streteched across several units. Some of these lived surprisingly longer than many realized because they were handed down to lower quality units in areas with less activities.
You definitely listed some good choices and others were quickly outdated by new variants or other new models and did not see enough action to warrant the work it would take to get them into the game... for as little as you would see them.
A few notes on some of these planes...
Airco DH-9 - Deemed a disaster from it's first day on the front and not until almost middle of May 1918 did it finally see enough service to be considered reliable, and even that was a crap-shoot.
LFG Roland D.VI(a and b variants). Not many built and mostly given to the Bavarian Jastas, most notably flown by Otto Kissenberth while he was with Jasta 23b. Quickly replaced by the Pfalz D.III and D.IIIa type as they were faster and cheaper to build.
Pfalz D.III - replaced quickly with the D.IIIa variant due to MG mount redesign and larger engine. Did not see much service, and only rough 260 built. Was inferior to the D.IIIa
Siemens-Schukert D.III - Used only by JG II (J12, J13, J15, J19) One month is all you get. The engines basically blew up or seized and they were sent back to factories a month later in late May 1918. The SSW D.IV would be better and saw enough action in upper number Jastas to warrant being in the sim.
Morane Parasol L is already in the game as both the MS and Pfalz versions. The LA only added ailerons and was quickly replaced as it was not effective as compared to what was being produced at that time. The P version would be cool to see.. the MS.24/26. Rounded fuselage and all.
Morane Saulnier Type N (Bullet) - would be cool...although not long for service and VERY limited numbers in use.
The rest are good choices that would definitely benefit the sim in many places.
I lost track of how many times we've all tossed plane types around that we'd love to see in the game, but I do agree with many you listed. An AEG C.IV would be nice as well.
https://en.wikipedia.org/wiki/AEG_C.IV
