The one big advantage those heavy peltasts have is armour/shield rating. However, with friendly fire the way it is, you can't use HP's to proper effect, nullifying the defensive advantage. HP's are an interesting comparison with velites. Velites get a 7 missile rating, same as the peltasts (and both get 5 melee. Velites get a lower armour/shield stat as they should. Another small advantage of the HP's is that they are "highly_trained" vs "untrained" for velites and the greek archers.

I'm already on record about the archery missile rating being too high across the board. I don't think an arrow should get the same missile rating as a javelin. Why? First, historically in this time period, javelins were more effective military weapons than archery (early on, the entire Punic War time frame...this changes some time around the Marion reforms or later.) Second, from game balance, the archers have more range and 5 times as many missiles. Third, if you had to make the unfortunate choice of getting hit by one, which would you chance: the javelin from a "highly_trained" peltast, or an arrow from an "untrained" archer with a self-bow? (I'm making the assumption that "chance of a hit" differs from the missile attack rating.)

The archer "flaming arrows" option really should make all archer units cost a hundred more apiece, plus considerably more upkeep. Heck, it is one of the few anti-elephant devices available. And they also will rout just about any unit that has poor morale.

If friendly fire is fixed, then HP's and other skirmishers begin to have a useful place on the field. Archers benefit as well, but by less of a margin since they are meant to be used at range, not up close like javelin skirmishers. However, to fully address the problem, archery needs seriously toned down as well. They should be good for specific tasks (at least early on) but less useful than javelin units on the field. If late RTW archers (elites) were as effective as the present "vanilla archers" (with vanilla archers far less) then it would probably be more representative.