Factories are not the newest thing ever. I believe Dave Shiels or somebody was running a pair in one of his Death and Taxes decks last year? I tried them, and you'd be surprised how often the factories get you there when all your other plans start to fall apart. Factories can fuel a port, cast your artifacts, then pick up a sword and beat face if the time comes. I don't hate them, but I'm not running them right now, because the metagame isn't as grindy as it was around that time last year.
Don't underestimate the Horizon Canopy (aka "the get-theres"). Canopy is awesome synergy with your enlightened tutor (tutor up and draw all in the same turn), and it's a precious little smidgen of card advantage for a deck that could sorely use it. They put Griselbrand into play and you don't have an answer? Punch the canopy and hope to draw a swords. Shit has happened to me before when I was on the Griselbrand deck. Same story with Cavern of Souls; you don't have space for more than 1-2 of them, but they can truly work wonders for you in the right matchup. Cavern's sort of a fifth vial (uncounterable) effect in a lot of legacy matchups.
Flagstones we've spoken about on this board before. They're nonbo with your Rest in Peace, combo with your cataclysm, and a juicy wasteland target for those looking to gain tempo by wasting in your upkeep and leaving you with a tapped plains for the duration of the turn. I like 1 main (-1 plains) right now just for the potential cataclysm synergy.
Ghost Quarter is (in my eyes) a different build of the deck. If I was running ghost quarters, wastes, and ports, I'd also want probably 4x leonin arbiter for the legit strip mine, and I'd be doing it in a metagame where I knew for sure that everyone was on combo or 3-color decks, since that build does slightly worse against monocolor non equipment/non-combo decks.
Tower of the Magistrate is a cute trick for having an uncounterable answer to their bskull/equipment. I feel like that's the land's only appeal, and it's too marginal to get me excited. I honestly think it's better for beating D&T than it is for helping D&T beat opponents, so if your meta's full of the mirror it might not be a bad idea, but I personally like manriki more. Same deal with Eiganjo Castle; it's just too corner-casey to junk up my main. Especially when the only boltable legend in your deck is thaleea.