Use of Thureophoroi

[Muskelsteffen]

Although I've read plenty about phalanx and the manipular system I have no idea for what reasons the thureophoroi exist and so how to use them.
I mostly play as a Diadochoi-state and so I have to decide to let my sarissai be accompanied by hoplites, some filthy celtic bastards or these thureos spears. Since the hoplites and foreign dogs seem to be better in melee I had never used the thureophorpoi. Was this a fault?

[Slaists]

They should have heavy throwing javelins similar to what legionaries use: so, a heavy missile impact (as opposed to light javelin impact) fast moving hoplite unit. I guess, not implemented that way in the game. Europa Barbarorum mod to RTW 1 has them right in my opinion.

[Sandraker]

They're supposed to be a mobile blend between a Peltast and a Hoplite capable of adapting to many roles on the fly.

Instead, they're slightly subpar infantry.