Republican Army

[Mitra]

Vegetius quotes from various sources, true. Somewhere he apparantly found a reference to antesignani having lighter armour than ordinary legionnaries. That much should be certain. I don't think the tekst permits replacing antesignani with another category

But they aren't placed on the battle line where the velites role is cover by "scutati (qui) plumbatis gladiis et missibilibus accincti",( the animal cap can be make reference only to signiferi or and anachronism of velites) . This make sense if they are the Joseph and Arrian general bodyguard, not a front line corps.

so there were special arms for antesignani![

Not necessary, the name for a category of arms cannot derived a priori from an antesignani corps.Like for the men the sense can derive from different concepts

Then why does he not say principales? The words are almost mutually exclusive. The most important principalis of the century was the optio, who certainly stood behind the ranks, rather than in front of them

Dionysus of Alicarnassus call promachoi, the men that in same episode in Livy are the duplares and the signiferi (all principales), the same tribunes are in frontal zone just before the clash. Promachoi in greek indicate "they that fight before the phalanx". The optio is an exception due his role. On can think in Phil. 5.12 the sense is not only principalis but principiis in general.

Cicero make orations, is normal to use archaic or strange forms; why he use "Phil. 2.71 “fueras in acie Pharsalica antesignanus;" at place of commander or officer?
Rhetorical necessity.
Cicero can think the public from the context can distinguish the sense.

No, it's translated as "most active", but that part of the translation is not mine, and is it is not central to the argument either

Sorry, for error i'm making reference to precedent concept of special infantry at place of velites.

The latter is correct. About the rest: I'm talking about the Caesarian period and as I already indicated, I think that antesignani meant something else before and during the later empire. Therefore the fact that Livy uses it differently is IMO beside the point.

The problem is that antesignani cannot be a precise technical word also in Ceasar. For the same job of 3.84 in Bello Africo Caesar take 300 normal legionaries for legion maked expediti.