I was going to suggest evasion of some sort, but I think you
may have that covered. For example,
Temur Battle Rage would be crap if you're only hitting the double strike, but I suppose you probably won't be casting it without getting the trample as well 99% of the time, so you're good there, and this should be your answer to large creatures as well...this and making sure your
Atog is larger!
On the other hand, I think I'd prefer
Fling to
Shrapnel Blast. If you get critical mass on artifacts or Myr Retreiver, an
Atog could get a lot bigger than the 5 from
Shrapnel Blast, and if you can send that straight to the dome you will probably close out some games (make sure you sac the
Great Furnace's to the
Atog while
Fling is still on the stack!). But there really isn't anyway to know for sure until you start playing it and reply here with your results!
On other notes, I drew some sample hands, and I am a little uncomfortable with the curve. Sometimes it draws fine, an implement (great choice here!) into
Atog and
Servo Schematic (also great synergy!), but other times I have 2 Atogs, and some 3 and 5 mana artifacts. This could just be variance (play it and you'll know for sure) but I really think you'll want to be brutal in cutting out every artifact that doesn't have major synergy and low cost. You'll really want this deck to be explosive and close out before they can cast removal or good blockers. Specifically, I'm not sure the
wellspring is good enough, even though there's the same mana:card as the implement. Maybe cut the
Scrap Trawler (though the 3rd creature is important, see below), and
definitely cut the
Ugin's Nexus: they both have some cute combo-like synergy with the 'togs, and it will be fun to pull it off, but I suspect this deck needs to be more cutthroat with your mana.
Also, I'm worried about removal. I play a pauper deck that also relies on combo-ing off a creature and it's functional reprint (Nivix-kiln fiend.) It's a super fun deck, (and I bet this will be too) but let me tell you, 8 creatures is not enough. I back it up with Delver, and have at a minimum 4 protection spells in the deck at all times, and I still lose a decent amount by having no creatures on the board. Thus, I highly recommend finding some (cheap) artifacts that protect your Atogs somehow.
I'll leave you to decide exactly which ones, and how to slot them in, but you'll have games where you need to find a way to keep that last
Atog on the board, and popping a
Glaring Spotlight is probably the way you'll do that.
Good Luck, and let us know how it works out!