They're not a terrible idea, just not a great one. Really, their role is filled, and better, by other units in the codex. Make that codexes, because there are allies and Escalation and pretty much all bets are off.
But this is not a rules blog, it's a modeling blog, and the models are awful.
So, as I take pictures of the latest raft of models to join my Necrons and Ultramarines, I've been thinking about them, and have basically whittled down the choices to two:
Choice the Firste: they're giant powered suits, more akin to a landmate than an actual Astartes suit. This necessitates a new look for the model along the lines of the SM aesthetic, ie "building out" the existing Centurion model with in-proportion arms and legs. Basically, a custom that looks more like the actual artwork.
Choice the Seconde: they're Terminator armor fitted with heavy weapons (and support hydraulics for them) I don't mind this option, because Terminators have been a viable heavy weapon platform (albeit a fragile one) from the get-go.
Choice the Thirde: is, of course, to move on to another project such as... shit, I dunno, an Outrider for the X-wing miniatures game.
Any thoughts, folks?