Is there any indication that these ships are redesigns of pre-existing elements or that they might be newer designs that one would have possibly never hoped to see in Halo: Combat Evolved with its sole visually depicted Covenant vessel?

There's more to a fleet than carriers and battlecruisers and nothing to suggest that these ships are frontline-vessels that would usurp the standard Covenant fleet composition to which we have known for years. It's kinda jumping the gun a little, especially considering that with the notable exception of Forward Unto Dawn, 343i seems to have taken few totally drastic liberties with the designs of starships. So much so that a light cruiser variant was merely a scaled down original CCS and the Phantom was simply given a new type number for Halo 4. Other things have been seriously remodeled and with little explanation or need, but it seems like you're going a little overboard with this at the moment.