Slitherine

What does the panel think about Thracian MF. Is it better to use heavy weapon rhompia or offensive spear ?

Depend of the army around

Thinking of getting some to augment my Alex & Successor pikemen, probably be used in open play more than themed.

With my alex mac, i choose the LS, Sw as they're not impetuous, can give a good delay in one bad going and are a nice support.
the HW in terrain don't fight very often armored troop to be a good choice and OS are impetuous and may fight when you rather like to see them protect the flank of the phalanx.

When I was using my thracians as offensive spear, I would frequently put them in terrain. If I recall, Med Foot will not charge out of terrain if you don't want them to, so the entire impetuous would be moot.

Then again, I am frequently wrong with the rules, at the worst times...

If they are completely in terrain they will not charge if they could end out if it.

Sadly, your phalanx have not always a terrain to flank them !
And your LS,Sw are better in town or other difficult terrain, than OS

I find OSp to be useful in some circumstances, but the HW seem to fare better overall for me. It's the cav that's the decision arm in this army. Plus, take all the skirmishers you can get.