Abevan

For me, a big indicator that this might be the case is the fact that the only known worldhopper from Scadrial happens to be an atium misting...

Apologies if this is mentioned, but what speed could you get the coins to? Are they accelerated the same as if there were no bubble and so would be moving incredibly fast outside of it, or are they accelerated the same outside of the bubble either way, but from inside you get much longer to push, resulted in the same high speeds (just using more steel)?

Personally I would like to see Kelsier as the villain in the second trilogy. Given what we know about the second trilogy it's possible, particularly when Kelsier's nature is taken into account.

With regards to steel being less flexible than Kevlar etc, wouldn't that mean less impact damage to the wearer, as a larger body area would be affected by the armour? Also, a Lurcher would probably just have armour covering his chest and so could go without the rest of the plate, lessening the weight carried even if balance now becomes more of an issue. And as for being distracted by bullet impacts in the quote from AoL, Wax fires all six shots at the lurcher in rapid succession, chances are all he had to do was brace for the impacts.

You could but the bullet would spread out as the push originates from the Coinshots centre of mass. Yes, they're going to be more powerful, but if your shots are all wildly off target all you would do is cause more collateral damage. Better to have the Coinshot holding a gun for just that extra power/speed (if it's needed at all). I can't tell if you've read it or not from your post, but if you haven't I suggest reading AoL, the main character happens to be a gun-wielding coinshot.

The atium itself isn't affected by Allomancy, just the crystals that generate it. The processing is just removing it from the geode and maybe combining/dividing nuggets. There's also the fact that Kelsier would have had to get his hands on raw atium from the pits in order to make the malatium Vin uses, as you wouldn't be able to use the electrum/atium alloy to make it.

I was under the impression that Lerasium (and the alloys) had effects beyond simply turning people into Mistings/Mistborn. If that's the case, wouldn't a Mistborn burning a Lerasium alloy just get the additional effects?

So the coinshots/lurchers in the air can only use the ground team as anchors? Definitely an interesting idea, particularly when you consider opposing air crew attempting to disrupt the ground crews movement. You could make it more interesting by having another ground crew above instead of the metal beams. Mostly I think that there would just be the addition of physical boosts to the sports we play in the real world (or variations of them). Only coinshots/lurchers have abilities totally unique to anything we have here. The real interest would be in what compositions of Ferrings/Mistings would be on the teams.

If this were the case, could it open up interesting possibilities with "Feruchemy for hire", essentially turning anyone into a compounder by buying the filled metalminds of the feruchemist?

Given that Malatium has a symbol, I'd suggest that the other unknown symbols are probably other Atium/Lerasium alloys. In addition, Malatium is only the second symbol aside from Lerasium to have a disconnected element.

On a somewhat related but also rather silly note, how does the regrowth and hair (and nails etc) work? If it's regrown with the other healing, Miles should be constantly producing hair at a rather fast rate. If not, he should be partially or completely bald, due to the times it's blown/burnt off. I can't remember any specific reference, but it seems like it grows to a certain point and then stops, which doesn't really make sense unless healing specific areas is possible.

As far as I'm aware the number of metals would be exactly 50, possibly 51. 16 base metals, Atium+16 alloys, Lerasium+16 alloys, then possibly an Atium/Lerasium alloy.

For your second question, storing weight is more storing gravities effect on your mass. I believe going around at half weight would store the same amount regardless of how much you weighed at the time,

The shards themselves survived, as quite clearly shown by the fact Sazed now possesses (for lack of a better word) them. The only thing to be destroyed was the two consciousnesses, his own and Ati's, both of which belonged to originally normal men. The idea that it could wound but never kill holds some merit, as regardless of Vin's decision Elend would have lived and we don't really know enough about the earlier attack to establish exactly what happened (I believe he intended to attack Alendi?).

But if this is the case, could the original Preservation not have destroyed Ruin in much the same way Vin did, as it would have led to the same preservation?