Is there really a use for missle units?

[stupac]

Well I don't control the baleric isles I do have Krete, maybe I will recruit some Kretian archers when I get the marian reforms.

You can hire them as mercenaries all over the place, which I think the romans frequently did. You can hire them for certain on sardinia and corsica, and I think also in sicily, iberia, and north africa.

Edit: why wait till marian reforms, you should be able to hire kretan archers in level 4 local MIC. Though they are pretty worthless against armored enemies. At least slingers get armor piercing.