All worthwhile points, Cutlex.
For whatever it's worth, if I had to answer the questions you posted, I'd say:
I. With the restrictions of Chalice of the Void and Thorn of Amethyst, Shop decks have to find a means to answer Outcome decks while having fewer means of doing so. Outcome might exist in a four Chalice, four Thorn, four Sphere metagame, but it would look different than it does now. It would probably have more lands, and a few less zero drop fast mana pieces.
Blitzkrieg Shops would love to be able to run something like Null Rod while presenting a clock to the opponent, but that's a tough ask, as the creatures available to you across your 1-4 drops are awkward. What's a great three mana Shop Aggro creature? In the first iteration of Blitzkrieg Shops, I had Etched Champions in part because your three drops kind of suck. Porcelain Legionnaire is a two drop, Phyrexian Metamorph isn't a threat unless you've got one already, etc.
If you're going to run Null Rod, you have to build your whole deck around it. Null Rod doesn't stack well (you never really want more than one), doesn't present a clock, and cuts off a lot of options for you (cards like Steel Overseer, for example), let alone what it does to your mana (as you're going to be running eight SoLoMoxen).
The trend since Lodestone's restriction seems to have been a race to the bottom - to run the most efficient (re: under-costed) Shop deck possible. Something that's hyper-aggressive, while having enough disruption left to stutter-step your opponent for the few turns you'll need in order to ensure victory.
Ratchet Bomb is something of a hedge. It addresses the Outcome decks (though not as effectively as Null Rod), all while it doesn't force you to rebuild your deck (due to your threats' lack of synergy with Null Rod). This particular strategy dates back to 2008 with N.Y.S.E. 5C Stax.
II. Foundry Inspector is a cool card that requires you to be incredibly dense with threats. The two approaches to him so far have been to either try and use him to reduce the upper end of your curve (making your Wurmcoil Engines, Precursor Golems, Hangarback Walkers and Walking Ballistas slightly more powerful early on), or to use him in a deck like Blitzkrieg Shops, where you're looking to make your two drops one drops, and explode on your opponent immediately after the Inspector hits. I'm still convinced that there's a third option that's some kind of crazy combo deck, but I don't think that's a Shop deck.
As it feels like it has been a race to the lowest, most efficient (and yet still powerful) curve possible, I'd suggest running them over running more expensive bots, if that's where you're at mentally.
III. The printing of Blightsteel Colossus had us running Sculpting Steel in our 75s. There's a better option than that right now, and if you're running Phyrexian Metamorphs with cards like Steel Overseer, there's a good chance that you're going to be able to get value out of them faster than your opponent will be able to catch up (with their higher curve).
IV. Mortarpod was an answer to Dark Confidant back in the day. It worked through a Null Rod. Dark Confidant was very, very good against Shops for a long time, and while many cards were played around with, Forino broke that out back in 2012 or so. If Dark Confidant is back, there are worse cards to have than that. It's cheap, can be used with a Rod in play, and does what it needs to do. There's marginal value to it in the Shop mirror as well.
Also, good luck to everybody at Champs. I'd love nothing more than to see a Shop pilot take it down. Roland Chang will be representing the New York crowd there, as neither Forino brother or I will be there this year.