Why would cavalry boost artillery? Aircraft do this due to their eye-in-the-sky capabilities, but I’m not sure I follow the connection of cavalry to my guns to shooting more accurately.
I do, however, see a connection between a successful overall attack (infantry, planes, arty, etc.) and a bonus to cavalry subsequent to that. If they served any unique use it was to take advantage of a breakthrough (much as what tanks would later do–or better, help create one).
Reading Norman Stone’s The Eastern Front (p.134-135), the mobility of cavalry divisions was a bit of a myth. Horses require a lot more food than men, and it caused massive logistical problems, especially train transport, for the Russian army. Given Russia’s already stressed rail infrastructure, all those cavalry divisions posed a strategic problem in addition to their tactical advantages.
On the other hand, cav divisions had their own organic artillery and machine guns.
The Middle East and German Southwest Africa (camelry, too, here) were also important places for cavalry or mounted infantry. In German East Africa, horses didn’t last too long due to disease.
Where could you find a game piece to represent cavalry? I’ve not seen anything that fits the 23mm size very well.