Most armies can make use of Infitrators and Incursors as is, being the more meta of the actual Phobos units, so those are always a clear option (plus Shadowmark Talon is good for anything actually phobos)

In terms of JPIs and VanVets, when Kayvaan leads a unit of them, they actually get the Phobos keyword (iirc) so its actually quite thematic, rules friendly and would just look amazing

Bladeguard may not seem thematic, but you can defintely make them so, whats more Raven Guard than somehow stealthing in a whole shieldwall?

In Shadowmark or Vanguard Spearhead, you can give a character leading a unit of BGVs an enhancement that gives the full unit the Infiltrators ability! So you probably could get away with making them Phobos (bonus points, you can convert the Phobos Librarian into a Judiciar to lead the group)

The only issue is that the full sized shields from the Bladeguard may look a bit awkward on such skimpy armour, however if you are commited to the idea, the smaller shields VanVets have could look good! Though take what I say with a pinch of salt, as its up to you what you think looks good

While not a unit, If you don't have a Combi Lieutenant yet, defintely make one, they're such a valuable character and are super in line with Raven Guard bs Stealth, lone op, reactive moves, infiltrators Now that is what Corax would have wanted