WF, you might want to seriously consider this idea.
plastic aztecs are pretty much the ONLY way you could make a proper aztec army ...
Conquistadors are a good start... the figures would also be useful... to medieval, renesceance (sp), and even napoleonic gamers. ...if it was called ' European Infantry 1450-1500... the same set could be marketed to a new audience, haha.
I think this could help the marketability of this set. While I have not yet done it, but "when" you (WF) begin researching the Conquistadors, along with the 'standard' Spanish Conquistador helmet, I strongly urge you to research the next "most common" helmet, cap, or head cover if you will, of european armies of this time period.
With this information, at the least add that "other" most common helmet of the time. This alone will give gamers a reason to pause and think..
"hmmm, just like that great WSS set. I basicallly have either of two (or more) armies in just one set. Ok I have to have this set!"
See.. its working already.
But seriously, it may be possible by just adding one, or if you can.. two "helmet' options in addition to the Conquistador helmet. You may open a much wider market door here.
Oh well in for a penny in for a pound.. might I suggest the box could be marketed something like this.
And european infantry of middle 14th to the 15th century."