Nobody seems to answer historical about Greeks. Maybe theyre experts have gone to some distant, remote place.
Yesterday I asked about ap for sarissai - nobody answered.

I could only say I support your point - it's very hard to wield even 3m spear with one hand, especially in phalanx, as the spear has to be hold in the point of gravity so it means 1,5m space both in front and behind is needed. This means you just can't make one hand spear longer without loosening formation.

It seems that Iphicrates had to use (and created) some kind of heavy peltast while fighting in Egypt - he had only peltasts and needed some unit to counter persian cav and heavy inf.