My wish list, all are typical and some indispensable, many have application up to and into WW2. With the exception of the 4.5 " How nobody makes any of these
British guns.
4.5" QF Howitzer: Yes Reviresco do one but
.
3.7" Mountain gun (ok so I've half made one but it's not for sale) Great War, NW Frontier, Burma and NW Europe in WW2
60 pounder. OK very ambitious but hey super cool!
German
7.7cm FK 16 Field gun, how about some variety chaps?
10.5cm leichte Feldhaubitze 98/09.
7.62cm Infanteriegeschutz. All those ranges of stormtroopers and no IG. Odd really. Gamers love toys, this one is one of those rare bits of kit which really should be fielded on table.
7.5 cm M15 Mountain gun. (OK its Austrian I know) Austrians, Germans, Turks lots of potential use, even WW2 Gebirgsjaeger.
Krupp 7.5cm export field gun (various labels but essentially the same gun in service with Belgium, Italy, Turkey, Japan etc etc) It's an easy conversion from a 7.7cm Fk98 but God knows why someone doesn't make one as a variant.
French: Mle 1878 120mm gun. It's so ugly it's beautiful
Russian: M1910 122mm Howitzer. Russian army = Guns. Great War, RCW, WW2
I could add the various Italian field pieces and some archie but I was just looking at guns to go with exisiting figure ranges. It's a little frustrating that everyone makes the same 3 pieces (4 if you add minenwerfer). I've given up on fielding caissons. I now use ammo boxes/ crates to mark the location of the gun teams. Fortunately I enjoy scratchbuilding so my artillery park grows apace but I woild have thought there was a market and plenty of cross over for most of the items I've listed.