Artisan of Kozilek, Ulamog's Crusher, Myr Battlesphere, Staff of Nin, Spine of Ish Sah, would be my next five.
Smokestack is best when you have a permanent that makes lots of other permanents. Or a bunch of low-cc spells. I don't think it would be good in your deck... too slow, and you need your permanents just as much, if not more, than your opponent needs theirs.
Mimic Vat... not sure you have enough creatures, nor do you have enough removal, for this.
Would also consider Boseiju and Urborg, Tomb of Yawgmoth.
Would also add Tumble Magnet and Welding Jar. Tumble Magnet is only good for a short time, but that time is turns 3 through 5, helping ensure you get a turn 6. Welding Jar is just a hunch... but I play a Slobad deck occasionally, and regenerating artifacts is pretty useful.
Static Orb is great against decks that attack with multiple creatures (i.e. half the metagame). Fun stuff too, with Clock of Omens, Krark Clan Ironworks, Tumble Magnet, etc., too. Storage Matrix also worth considering, though not quite as good as Static Orb.
Relic of Progenitus is a no-brainer to me; worst case it cycles.
Also, add Clock of Omens. It will immediately become perhaps the 5th best card in your deck. It's outrageously good.
what you think about?
I also removed maze for another panorama.
It's an uphill battle, trying to play colorless. My hunch is that in the majority of competitive 1v1 games, you're not even going to cast your general. So that's card disadvantage before you even roll to see who goes first. On top of that, you're by definition using a worse cardpool than every single player you play against.
At least Karn, Silver Golem gives you a nice wall that you'll be able to cast most games. And Emrakul most likely gives you a much better chance of winning than Kozilek, provided your opponent somehow lets you amass all this mana.
If you're dead-set on colorless though, the one card I'd recommend is Memory Jar. Also perhaps Trinisphere.
I'd also significantly cut down the number of high-casting-cost spells in your deck. Nullstone Gargoyle probably hurts you more than your opponent. And Possessed Portal is most likely going to be in your hand when you're behind.
My driving concepts about the deck are
1. every play should be game-warping 'cose the threat density is very low with 30+ mana accelerator
2. Consistecy & redundancy over fancy comboes. Though Kozi has draw4 triggered the deck has 0 manipulation and very costly tutoring ( Planar Portal - if played) or Drawing.
3. Never miss a landrop. Every landdrop you miss is -1 mana cc0, with the defoult 40 lands you're going to miss a landrop about t5-t6, i play with 42
Fast eldrazi with annilhator trigger is our best removal.
Beside this i have some questions about your list:
1. How did you feel "stack" package in game? before winter orb banning i played
and it was very cool.
2. How did you feel Spine - Ironworks ? a recurrable removal is very strong but i always felt 2card comboes hard to set-up in monobrown
As a general consideration however i think that a deck that could be completely turned off by a card ( null rod ad you pointed out ) is difficult to be competitve. Especially with the bannings of the best accellerator