Advice on Homebrew Subclass: Ferroknight

Some interesting ideas here! I've a text wall of comments (not intended to be negative, just thoughts on possible tweaks/improvements):

Magnetized Weapon: Mechanically you may have a few issues to address; is this intended to allow you to wield two pikes with Dual Wielder? How are two-handed ranged weapons (like a longbow) intended to work (do you want a fighter running around with a greataxe in one hand and a longbow in the other yet still somehow firing the longbow)?

In case it helps, I've got some homebrew for large races and have been refining a similar rule for how they can wield a single two-handed or versatile "medium" weapon, and the latest iteration of the rule is:

• You may wield one medium sized or smaller two-handed or versatile weapon in one of your hands with the same effectiveness as if you were wielding it in two. You may only wield a ranged weapon in this way if it has the loading or reload property.

Just to let you see how I've setup a similar rule after a bunch of playtesting and iterations, as you could maybe tweak this to fit your intended theme.

More generally though I wonder if there should still be a benefit to wielding a weapon properly; for my large races wielding a medium weapon like this is an alternative to wielding a proper "large" version of the same weapon which deals either +2 damage or has reach, so you have a choice between a large greataxe, or a medium greataxe plus shield, which keeps the weapons somewhat balanced. As it is your current rule makes all other weapons redundant as they simply deal less damage with no benefits of their own, so I think there should either be a benefit to still using two hands, or a benefit that applies to other weapons to balance it out.

Rail Weapon: I'd maybe tweak the recall wording a bit to something like "You can magnetically pull a metal weapon you can see within 60 feet into a free hand as a bonus action. If the weapon is held by a creature, it must make a Strength saving throw with a DC of 6 + your proficiency bonus to prevent this, or a DC of 10 + your proficiency bonus if it is within 30 feet." or something along those lines? This way it scales, and makes clear this is a feature not just for your own weapons (there's currently a bit of a disconnect in the wording).

Magnetized Armor: Instead of eliminating stealth disadvantage, would it maybe make more sense to be able to doff the armour as an action, but then recall and don it in the same way as for rail weapon as a bonus action? i.e- if you need to sneak in somewhere, you'd doff your armour, stealth in, and if combat occurs your recall you armour as a bonus action to reattach to your body (like in the later Iron Man movies)? This would feel more "magnetic" IMO, though it might need some restrictions (unobstructed path for the armour, maybe a range limit)?

Field of Polarity: I like this idea, but I wonder if might make sense to make it a bit weaker but give it more, scaling uses (e.g- proficiency uses), maybe limiting the disadvantage to only attacks against yourself (so it's a purely defensive feature rather than an aura debuff)? Also I assume that the effect is intended to move with the player, but this may need to be specified?

Hold Armor: Interesting feature! The DC should probably be based on something (number + proficiency bonus?) so it can scale up at higher levels. Could probably use some clarification on the number of uses; is it five uses per long rest, but you can spend as many as you like as a single action? I'm a little unsure about being able to hit five targets at once on top of Field of Polarity, it might make more sense for this to also be proficiency uses per long rest, but a single target at a time (effect ends if you choose another target) but you could still potentially use this to lock down a single armoured target even if it saves (by triggering the effect again)?

Magnetic Storm: As with Field of Polarity this probably needs to clarify if it moves with the player. I'm also wondering if it might make sense to tie it to Field of Polarity, i.e- once per long rest you can spend one use of Field of Polarity, increasing the radius to 25 feet and gaining the push/pull and can't leave the area effects?

Ferrous Flight: Fun feature, but should there be a limit to how many creatures can be given flight in this way?

One overall thought about this sub-class though is that it's very campaign/encounter dependent; very powerful if you're facing bandits or whatever with metal weapons and/or armour, but against creatures without any metal you're only really receiving the 3rd and 18th level benefits, everything else is outside your control. It might make sense to have at least one of the features be more general purpose. For example, Field of Polarity could include a cloud of metal filings so it can effect enemies without metal, and the same for Magnetic Storm?

Anyway, these are just some initial thoughts; hope I don't come across too negative or nitpicky, as I like a lot of the ideas in this sub-class!

Magneto is a comic book character.