Oh right, we can use Mimic Vat to get two uses of Engineered Explosives. But, don't we run into the danger of using both Explosives to kill Moggcatcher? We just need to bounce Moggcatcher once to create a bank of Bloodbond March triggers.
I'm thinking that Metallurgeon still goes infinite. We can use our Metallurgeon tokens to create a stage, with Bloodbond March triggers on the top. We can then crack an Explosives to destroy both Wirewood Herald and Metallurgeon, creating tokens of both. We use the Wirewood Herald trigger to return it to our hand, and then resolve a Bloodbond March trigger to return Metallurgeon to the battlefield. Use the Metallurgeon token to extend the stage by a couple layers. Cast the Herald to bounce Moggcatcher, sacrifice Goblin Dark-Dwellers, creating a token copy, make the hyperstage transition, get Explosives back with Rebuild, and sacrifice it again to destroy Herald and Metallurgeon again. Create a couple more layers of the Metallurgeon stage, play Moggcatcher for Bloodbond March triggers and destroy it with the Herald, and create a Moggcatcher token. Tap the token to bring back Dark-Dwellers, and get Explosives back, going back to where we started, but with four more layers in the Metallurgeon stage.
Ahhh, I see. I'm not 100% sure that works, because the stack is getting very complicated here, but nothing jumps out at me as a clear problem, so let's see if there's any fix for it.
The first thing is, I wonder if this works to the same degree with the other option: cut Turncoat, and add in Tajuru Archer and Beastcaller Savant.
For clarity, the way this one works is: use an Engineered Explosives to kill Beastcaller, imprinting it on Mimic Vat and triggering Verdant Succession. Play Moggcatcher for Bloodbond March triggers, then make a token copy of Beastcaller, using the Archer's trigger to kill the Moggcatcher and make a hasty token. Then we shuffle the Beastcaller back in, and use the Succession triggers to get it back, which also bounces Moggcatcher. Critically, we can't use both triggers to get two hasty Moggcatchers, because of the severe timing restrictions involved.
There are two problems here: we have no way to get Tajuru Archer back after the megastage transition, and we only use up one Engineered Explosives in the same time frame. We could potentially solve all that by going back to the old Izzet Guildmage plan with Nylea's Disciple, but I'm not sure that plan actually works. Because Dark-Dwellers casts the instants themselves, not copies, I'm pretty sure we need some kind of [c]
Thousand-Year Storm[/c] effect to let us build the hyperstage, and all those effects go infinite when combined with Natural Order in the gigastage.
Failing that, we have to find some way to turn an Engineered Explosives into a way to get back Tajuru Archer in the megastage transition, without going infinite.
Hmm, we could throw in a third color, and have to crack an Explosives for 3 to destroy Tajuru Archer, which would waste an Explosives. That would nullify Centaur Safeguard, of course, so we need a replacement, but it could be a good way to solve those two particular problems.
Edit: Okay, so going with Tajuru Archer handles the problem of creating two Moggcatchers with one run through the combo. But, it still doesn't handle the problem of creating an unwanted Metallurgeon token. I believe you can do the same thing as what I described before: Create a stage for Metallurgeon, then each time you sacrifice Engineered Explosives to destroy Beastcaller Savant, you also destroy the original Metallurgeon, and can create a token copy of it, allowing you to extend the Metallurgeon stage. So I don't know how to handle this.
So, I had an interesting idea - let's say we wanted to go back to using Boggart Mob. We can target it using for example Godtoucher, but unfortunately Godtoucher also targets Child of Alara, so we can go through the megastage transition without spending the life. But here's a possibility - we could replace Mimic Vat and Horobi, Death's Wail with Soul Foundry and Brudiclad, Techor Engineer. So, instead of creating tokens by destroying them via Mimic Vat, we use Cowardice to send them back to our hand and imprint them on a Soul Foundry. Now, when we tap Godtoucher, we can target Child of Alara, but we can't destroy it.
It would be nice if we could now get rid of Mimic Vat, but unfortunately I don't see how we are going to create token copies of our enchantments. I had an idea that we could go back to using Splinter Twin and Crown of the Ages, but for now, let's just keep Mimic Vat in the deck.
For the moment, that still goes infinite, because it also gives haste to Mirrorworks copies of our artifact stage creature. I don't know if there's any way around that, but if there is, that's a very promising strategy!
With the infinite you discovered, if we can find a way to prevent copying Battle Cry: that way, we need a hasty copy, and to have the nontoken in hand, to continue. The problem is that the. I don't know how to build the stack up, since we can only resolve the non-copy card Rebuild. We can do it with the changeling tech, because each new Battle trigger can turn into one new spellcast, but that strategy has a host of other problems, too...