Hmmm, this sounds quite intresting, B0rsuk. At one point I myself toyed a bit with the idea of a slavic nation with heavy polish flavoring (winged hussars are irresistible
)
This also reminded me of my finnic/kalevala based nation idea I have been toying with lately (again). In fact I can see some similarities, namely Perun, the wise men/women and evil water spirits. I've even drafted up variants for all three ages but I'm kinda at loss because my knowledge about finnish mythology isn't so strong in the end.