I purchased the Essex Army pack II/49 Marian Roman. The pack included Psiloi that had bows. Just because they have bows, that does not mean they shoot doing the shooting phase, right? Psiloi's don't shoot, only Bw,Cb, LB do? And this is the same for LH that have a bowman on them?
It gives you a bit of artistic flair to put whichever figures you like on to a Psiloi base. I have some with both an archer and a slinger shooting from long grass for example. At the end of the day they are a Psiloi base no matter what weapons they are holding.