I've had a mid-range-y Marchesa deck for a while, so I'll chime in.
Mahadi I've found to be kind of underwhelming, but it's not bad. I'd prefer Dockside Extortionist, and any of the various 1-3 CMC creatures that either make a treasure when they ETB or die. There's also
Pitiless Plunderer who doesn't care about when your creatures are dying, and can be used as either a combo piece or to fuel a big turn, since the treasure comes immediately.
Danny Pink looks fantastic here.
Uncivil Unrest has been really good.
Maskwood Nexus and Arcane Adaptation won't turn your creatures into artifacts, because 'artifact' isn't a creature type. Unless you're leaning VERY heavily into tribal AND have some high value off-tribe cards you feel need to conform to that theme, these aren't worth it here anyway.
Encroaching Mycosynth might be worthwhile, but I feel like it just makes it easier to deal with your permanents. I'd recommend
Liquimetal Torque as both a mana rock and a way to turn something into an artifact when you need it to be. The biggest boon of EM, I think, is protecting your value creatures that aren't artifacts, and can't attack well, but I don't know that that's necessary.
I'll also note that it looks like this list hasn't been updated in a while, and there have been some pretty significant artifact-themed cards in the last year or so that might make it in.