You have to keep Sen's Triplits...she has all three of your colors.  You owuld have to go mono blue if you went with Thada.  As for cutting cards, it all depends on how you like to play.  If you want some of the top end cards then you could easily cut a few of your artifact mana cards for better stuff like Gilded Lotus, and so on.  But you seem more like the kind of guy who likes to go unconventional.  Plus going high end costs more money.  You know who would be a great fit, the Grand Architect.  Not a mirfolk, but uses your artifact ability to a tee and he's not costly.  Cut Argent Mutation and replace it with Liquimetal Coating...does the same thing but sticks around AND it combos nicely with Master Transmuter.  Protomatter powder and Cumber Stone could go...you already have ways to return artifacts.  Maybe add Buried Ruin and Expedition Map.  The Map can help you find Academy Ruins which is crucial, and Buried Ruin is a land that you can sac to return an artifact.  Cut one of your lands for the Buried Ruin.  Even with a hundred cards its so tough to cut....

Mass removal if your playing multiplayer: Day of Judgement, Decree of Pain, Black Sun's Zenith, Damnation (again for those with money:p).  For heads up stuff like Doom Blade, Murder, and of course the all time greats like Swords to Plowshares, Path to Exile, and so on.  

That's why I like the format.  It allows for all your favorite cards and increases the value of bad cards in other formats because with a hundred card singleton you have more time and can justify over costed cards.