I would really love to see Madred's Bloodrazor in the game again

In some form at least.

For those who weren't around back in the day, Madred's built out of an AD/Armor Jungler item and provided Armor, Attack Damage, Attack Speed, and did 4% of the target's max HP OnHit. Now, I don't think that exact set of stats would be the way to go, especially since the magic damage did always clash with the physical. We've got BoRK to cover that niche now.

Instead, I think the AD could be cut from the equation completely. Madred's could move in one of several directions from there, depending on whatever might be the most useful route to take. I'm imagining here a pretty pricey item, just like the original Madred's was. Something that would provide a fairly nasty mid-game power spike, but would require a bit of time to get rolling. I'm going to suggest two different versions here, each with it's own obvious niche.

= Madred's Bloodrazor Provides attack speed, CDR, HP, AP, and- Eyes of Pain: You ignore 15 of your target's magic resistance. UNIQUE passive: You deal 4% of the target's max HP as bonus magic damage OnHit. UNIQUE passive: You heal for 20% of the magic damage you deal (1/3rd benefit on AoE effects).

So this guy would basically be a magic damage answer to Death's Dance. We all know Riot despises spellvamp for Mages, so this item neatly side-steps that issue by being an item that Vlad would never want to buy ever. It provides a third IAS/AP option to pair up with Rageblade and Nashor's while also granting something this sort of build is sorely missing, sustain. As an added benefit, Guise gets a second build path.

= Madred's Bloodrazor Provides attack speed, CDR, armor, HP regen, and- Point Runner: While near turrets, fallen turrets, and Void Gates you gain 20% movespeed over two seconds. UNIQUE passive: You deal 4% of the target's maximum HP as bonus magic damage OnHit. This bonus damage applies to Turrets.

Simply put, there's no good item to grab for demolishing Turrets if you're running an OnHit build. This design adds a nice armor option back into the OnHit menagerie that focuses on improving the user's ability to crush objectives. This provides it a niche quite distinct from Blade of the Ruined King.

Either of these items would be pretty solid way to get Madred's back into the game as something other than a trap item Marksmen don't want. One is clearly an option for AP auto-attackers while the other is a potent Diver item.