There's a number of 2-seaters that could/should have been done by now IMO, like the British FE2 and BE2 , French Voisin and German LVG (not sure about it's full name). All of them (or upgraded versions) were used until at least mid-1917 (long past their useful lives in the case of the allied planes).
In the case of the Albatros 2-seater (and pretty much all of the German 2-seaters for that matter), I think that since the game stats would be fairly close to the more recognisable (at least to the casual gamer) Roland anyway, they just stuck with that for now. Having broad types works well enough for game purposes, it's just pernickity folk like us that need to have the exact planes I did pick up a pair of Hannovers as generic Roland replacements from late 1917 myself. Nice-looking planes.
The Hannover is a nice plane (I assume we are talking CLIIIa, right?) but it is not the same type of plane like the Rolands, CL planes (Halberstadt CLII is probably the most famous of them, I have one of those myself) are made for strafing and scouting. They are a lot smaller than the larger C class that can take bombs and solve a lot more types of missions
A - Unarmed reconnaissance monoplane aircraft (for example the Rumpler Taube and Fokker M.5)
B - Unarmed two-seat biplane, with the observer seated in front of the pilot.
C - Armed two-seat biplane, with the observer (usually) seated to the rear of the pilot.
CL - Light two-seater, initially intended as escort fighters - latterly mainly used for ground attack.
D - Doppeldecker - single-seat, armed biplane, but later any fighter - for instance the Fokker E.V monoplane was redesignated the D.VIII.
E - Eindecker - armed monoplane - initially included monoplane two-seaters. New monoplane types at the end of the war designated as "D" (single seat) or "CL" (two seat).
Dr - Dreidecker - triplane fighter (prototype Fokker triplanes initially "F")
G - Grosskampfflugzeug - Large twin engined types, mainly bombers (initially "K")
J - Schlachten - Armoured ground-attack aircraft
N - "C" type aircraft adapted for night bombing
R - Riesenflugzeug - "Giant" aircraft - at least three, up to four or five engines - all serviceable in flight
I myself have only a single Halberstedt right now together with a AEG GIV heavy bomber and a Junker JI to use for anything except Scouts after summer 1917. I have comparibly about 20 german scouts from the same period, the planes are really hard to find but are a very important part of the game.
As for the argument that most people don't need the exact plane, the difference between the Roland and the later german C planes are rather big, in that case they should have scrapped one of the Albatross types instead because they look a lot more similar.
The fact is that we only have german 2 seaters from may 1916 to Aug 1917 and Allied from January 1917 to the end of the war. That just isn't enough. A allied 2 seater from 1916 (like the popular Sopwith 1 1/2 Strutter) and a Albatross CX or CXII or a LVG CV as you suggested (July 1917 to the end of the war).
While I think it is nice that they add the SALM plane in the next expansion I think they should have added 2 more 2 seaters to the next set, there is a huge hole where there is no 2 seaters from and there are very few to find even if you buy the planes from other sources. Hannover and Halberstadt are the only 2 german 2 seaters used post 1917 if you don't count Junker JI or don't order the really expensive and fragile resin kits from companys like SRAM.
As I see it is the big holes in the timeline right now a german scout from 1916, a german 2 seater post 1917, a british or frensh 2 seater pre 1917 and a lot of planes from the eastern front, there we basicly only have Albatross DIII, the Hansa-Brandenburgh CI and Spad XIII right now, not a particularly fair mix. The Salm and Aviatic will will even out things a bit and I agree with those 2 but the choice of Nieuport 16 sucks, it has no german scouts to fight against, just balloons and Rolandss, and france already had Nieuport 17 that only arrived a few months later.
There is many holes to fill in yet and my question is still: Where is my Albatross C class plane?