The Thraikioi Peltastai are actually exellent infanty. They're actually one of my favourit units.
But, as has been said, there are quite a loot of Thraikian units, so just adding another, that is basically the same as Thraikioi Peltastai, but without the javelins, seems pointless.
You have after all (pardon me, if my spelling of these names is incorrect):
Thraikioi Doryphoroi
Thraikioi Peltastai
Thraikioi Romphaiaphoroi
Taxeis Triballoi
Thraikioi Hippeis
Thraikioi Prodromoi

That is four infantry units, and two cavalry units, and in addition to this, you also have some Getic units. I'd say that the Thraikians are one of the more numerous and diverse non-faction roosters.