Not sure how much money (if any) you're willing to invest into this project, but I do have some suggestions.

First: Hovermyr.  It flies, it has vigilance, it costs only 2 mana, and it's an artifact creature. 'Nuff said.

Second: Why Origin Spellbomb?  I get that it's cheap, but it isn't cheap enough.  2 mana gets you a 1/1 artifact, 3 mana gets you an additional card.  You could just as easily put in a Myrsmith and pump out extra myr every time you drop an artifact.  Combine it with Glint Hawk and you can turn your Memnites into myr factories.

Three: Chimeric Mass.  Cheap if you need cheap; strong if you need strong.  It's hard to imagine this deck without it.

Four:  Gold Myr.  Take out some plains and put these in instead.  It's a 3/3 at your first Tempered Steel, and it means mana-ramp.  In a deck like this, I'd much rather have 18 plains and four gold myr than 22 plains, which will only slog up the deck in the late game, and can only come out once per turn in the early game.

Five:  Get rid of Precursor Golem.  If you're going to use golems, invest in some Blade Splicers - they're cheaper and stronger, even if they don't pop out three at a time.  One Volcanic Hammer or Dismember will ruin your Precursor's day, much less a Dispatch, and you don't even get the pay-off of using your own spells on him.

Six:  Oblivion Ring is nice.  Dispatch is nicer.  Ditch the rings and put in another two Dispatches and another two Dispense Justices.  Or just put in some more artifact creatures.  If you're really having attacker problems, put in Cathedral Membrane, or a Norn's Annex. 

Another interesting option is Darksteel Myr.  It's pricey for a 0/1, but it does not have defender, and with Tempered Steel can be a vicious attacker or blocker.