That is true, however I'm inclined to stick to my guns here. This pic shows a unit which is little more than Sloped frontal armour with a large cannon above and walker legs below. The Megalith, however, looks like it incorporates some battleship components too (the main cannons and the flatter surfaces on top), plus there's the bulk of that vehicle fabricator under the nose.
I have no idea. It certainly looks like one, then again it's rather hard to tell without knowing more about the artist's conventions (EG, while I can tell a melta, lascannon, autocannon and multilaser apart from warhammer, I am far less clued up in star trek and would fail to tell apart their weapons).
Nicely done! Love how u drew the legs and the chassis area. Great work!
But also, I gotta say, that Mech kinda reminds me a Mecha or drone off from 1 of the Supreme Commander teams I seen b4. Like maybe like 1 of the Cybran's drones I should say. But great work though, love it.