I think the novelty value of a tachanka set would guarantee reasonable sales, not least from people who have already bought Strelets Bolsheviks etc. Cavalry aren't really needed, as Hat already do them, and there's an Orion set of Red Cavalry in Budenovkas - other types can be converted from WW1 sets fairly easily.
By contrast a "classic" tachanka is not easy to convert; if you go on to Youtube and see some of the clips from, eg, The Nine Lives of Nestor Makhno, you'll see what I mean.
Our group has tachankas converted from assorted limbers and wagons, with crew and MGs added, but they are not ideal.
If I were producing such a set I'd make it two tachanka carriages, eight horses, two MGs and drivers/MG crew ... but it is a very tricky piece of work in this scale: then again it would be literally unique.
BTW on Youtube you can now see The Nine Lives of Nestor Makhno with English subtitles ...which has lots of tachankas in various episodes!