Why does Hector have this skill? What link team could form around him? He has wild card so can join myrmidon and thorokiti teams. But can he form a thorokiti link team taking the place of the thorokiti profile with the enomotarchos skill?
Yes, he can provide the Enormoustacos skill for Thorakitai, Myrmidons, or Dactyls as needed. He doesn't let you mix them in the same Fireteam though.
I would assume he could be the anchor for starting a fireteam as that was the case in N3 and to start an enomotarchos you require at least one model with the skill to make a fireteam of that type, but given the absolute dumpster fire mess of the of the fireteam formations and fireteam rules in general that mayu not be the case.
You can use Hector, Thrasymedes fto or Acmon to create a Thorakitai or any other link where Hippolyta can just join a link. I tend to stick Hector with a doctor dactyl and an engineer dactyl. I am real tempted to put Thrasymedes in a Myrmidon link as a secondary gun.
Thing is, even if Hector does have Enomotarchos, I wouldn't use him in Phallanx under normal circumstances. Mr. Eric Bana the Plasma Dealer has one of those "good at everything" profiles, so you'll want to invest orders in him during your turn. The +1B from Enomotarchos is nice, but not significative enough that I'd sacrifice the flexibility of vanilla Aleph in order to link him (If it was the 5-man bonus he can get in Starmada, it'd be a different story). What I'm trying to say is: if you're playing Phallanx, you can get more mileage out of the "middle of the road" profiles like Machaon, Phoenix, or Eudoros, but if you want to field one of the top dogs or solo profiles (Achilles, Hector, even Pat or Penny) you could do better with vanilla. Regarding your question (and as far as I understand it): the rules specify that, in order to create an Enomotarchos link, you need at least one linkable trooper with the Fireteam: Enomotarchos skill, and at least one trooper being (or counting as) one of the linkable profiles (Myrmidons, Dactyls or Thorakitai, without being able to mix them). Therefore, Hector brings the Fireteam: Enomotarchos skill to the link, then you just need any one Myrmidon, Dactyl or Thorakitai and you're golden.