honestly, i think you'd get better sales if you did the giants closer to the recent Reaper Bones size of giants.. so you can fit two or three into a kit. sure they're smaller than the GW and mantic ones by a fair bit.. but they're still 6 inches tall. (measuring my Reaper Bones 5 storm giant.. and while i haven't assembled it yet, the female storm giant from the bones 5 greek odessey expansion is similar size)
using say, a 120mm size or even a 100mm height would work just fine gameplay wise and still offer a lot of fun customization options. and while you'd probably need to spread one giant over two sprues, you could include a lot of customization options, especially in terms of decorative bits you can hang off it.
while having giants that are almost a foot tall might be visually imposing, being able to field multiple ones for a cheaper price is going to be attractive. and a lot of non-GW fantasy gamers are going to prefer the smaller more managable size, since most fantasy games outside of GW tend not to make their giants in "mobile mountain" in terms of unit size. (even mantic, wiel they produce a massive giant of their own, actually has trouble fitting their foot tall monstrosities onto the 75x75mm bases used by the game, not to mention major problems with them tipping over during play. especially the northern alliance and nightstalkers variants of the kit, which add a bunch of heavy resin replacement bits for the arms and head..)
