Oh yeah, precursor weapons are primaries aren't they ? That sucks. I don't think you can convince officer models to fight with something else (unless the appropriate skeleton does the trick), but at least you could make him use the fs_o_f_spearman overhand skeleton for it. Although I make my generals and officers use the "_fast_" skeletons, as the buggers often have to run back and forth a lot when the units change facings and such and if they pause to do that "yell orders and wave your weapon" thing, as they often do, they tend to end up lagging a whole lot behind.

Side note: for my Lusotannan generals I use the Spanish late bodyguard texture from Maximusminimus' Carthage mod. It's not really all that Lusotannan per ce, but in any case looks properly Iberian - if one now had to come up with justifications for placeholders, one could claim the bigwigs wear expensive and hence prestigious imported war gear.