Oh sure, and I don't want to give the impression about being toooo crazy with the mixing and matching. Differences did (usually) exist between ranged and melee cav, phalangites and peltasts, etc. But the differences between one handed weapon infantry such as a pure peltast, hoplite, spearman, swordsmen, axemen, etc. were likely rather slim and often non-existent in many forces. Weapons from the greater spear family tended to predominate as primary weapons among most non-Roman ancient forces (and even the latter were very pilum based) for a number of reasons.
You are completely correct about hoplites; they changed character drastically several times during their history and seem to have covered a wider amount of roles as time went along. The experiences of the 10,000 are a perfect example of this; I doubt that was the only time hoplites were pressed into slinger or another service as a tactical expedient. In the end ancient commanders were just like modern ones in the sense that they would likely use whatever forces they had on hand, even if they were not 100% ideal to solve the desired situation.
P.S.- I am working on some projects at the moment and will hopefully be able to announce a small one here soon. But when it comes to chariots the sources of Mary Littauer and Joost Crouwel dominate... for now.
And an intersting fresco from a recent Macedonian find dated late 4th century 325-300bc, the tomb contained an iron "Linothorax" much like Philips example, interesting in that it shows a range of troop types and colours: