Judging by their size, durability and the scope of the weapons they use, I'm gonna guess that Centipedes are meant to be tanks in all but shape while the Scythers are more akin to infantry. That said, both mechanoids moan and groan when downed, so the Centipedes do have some amount of voice modulation.
Maybe Centipedes are like Hunters/Mgalekgolo from the Halo games in that their communication is largely unneeded but otherwise possible. Hunters make guttural taunting laughs when they manage to kill you and the few times they are friendly during the original trilogy when playing as the Arbiter, they do make guttural grunts in response to you looking at them when close to them.
What do you guys think the mechanoids look like, in terms of artwork? The skirt on the Scythers along with their reclining posture implies to me that they are tracked gun platforms, and a great hulking 10-12ft (at least, judging by their ingame size) tall Centipede with the back mounted gun makes for an awesome image in my head.
EDIT:
Something else that came to mind is perhaps the ability to disable the AI of crashed ship parts with colonists that have high crafting, allowing dissassembly of the part for metal, recovery of the core and not waking the numerous mechanoids that are likely to be aboard. One could even go as far as to contemplate turning some of the mechanoids on after turning them friendly. They are robots after all, going all Fallout 3/NV on them and redefining their concepts of an enemy should be possible. That all depends on Ty's lore reasoning for them. If the lore says it's kay, then it's simply up to Ty to make it so, or expose the code necessary for modders to make it so.
DOUBLE EDIT:
Another thought. Drag back wounded Scythers or Centipedes to a workshop and fix them up to make them friendly. They are practically whimpering in pain when crippled, render them some aid and perhaps they would appreciate the repairs.
TRIPLE EDIT:
RAIDERS WITH SALVAGED MECHANOIDS. OH GOD THE HORRORS OF 50 MAN RAIDS WITH MECHANOIDS.