Well if Alpha Legion want a faster and more maneuverable craft that can outrun anything it can't outgun and requires less in the way of resources and would be more innoucous than norm then escorts are the way to go.
Except if they're chased by other escorts. Which may both outgun and outrun them.
The problem with the escort solution is: A) Escorts are made of tin foil. If you're going to have a protracted career as a terror of the space ways, it's not the way to go, since things can always go wrong. B) Almost all the current Escorts that are in the Chaos fleet list, with the possible exception of the ico, seem to be newer types of escort. Reading through the HH books, there does appear to be a few ship classes from that era that serve similar functions to the dauntless.
Further, if the new rules are going to allow chaos to take IN LCs anyway, why not have their own LCs?
(Flight of the Eisenstein was hair pullingly vague in a lot of ways)