Upping the 8 archer limit would be too powerful for Parthia and Saka rauka .

4 solutions: a) Special rule for sauros ( too complicated in my oppinion)
b) Addind some melee only cav in their roster (best option IMHO)
c) upping their merc limit ( only partial fix)
d) Downgrading the Scythian heavies from Hcav to Medium Cav( somewhat OP )