On Aghanim's interactions with other items...

So there were three forums this could have gone into, but I decided to put it here due to the ramifications of this idea.

Now, as we all know, certain Heroes get ultimate ability upgrades through the purchase of an Aghanim's Scepter. However, to perhaps add another level of interest to the game of Dota...

...what if, while upgrading a hero's ultimate was still reserved for Aghanim's Scepter, their OTHER abilities could be slightly buffed when buying certain other items? This could serve as way to scale heroes, giving them a power spike at some point in the game - this spike being flexible based upon when they want to pick up their 'upgrade' items.

Now, I suspect you're all finding this very confusing because I don't think I clarified accurately what I meant, so I'm going to provide a list of Heroes, and how they could have their abilities upgraded. I'm not suggesting to add a slew of new items. I'm suggesting this be tacked onto already existing items, and it vary from hero to hero. Perhaps it can be used as a consolation prize for being forced to go MKB on Sven as a second item... or maybe to just give Queen of Pain a nice kick in the lategame.

Abaddon
-Purchasing Assault Cuirass on Abaddon will increase the cast range on Aphotic Shield to 850.
-Purchasing Crimson Guard on Abaddon will also provide an aura effect to Curse of Avernus, with a range of 250 units for the aura.

Phantom Assassin
-Purchasing Monkey King Bar on Phantom Assassin will now give her True Sight on anyone affected by Stifling Dagger.

Naga Siren
-Purchasing Heart of Tarrasque on Naga Siren will reduce her base attack time to 1.55, and grant her 15 base damage.

Necrolyte
-Purchasing Octarine Core on Necrolyte will reduce the cost of his buyback by 50%, and the cooldown by 2 minutes. Before you ask, yes I am aware of the sheer aids this will cause.

Phantom Lancer
-Purchasing Abyssal Blade on Phantom Lancer will increase the damage his Juxtapose illusions deal to 20%, and increase their duration by 50%.

Terrorblade
-Purchasing Black King Bar on Terrorblade will reduce the bonus damage his illusions take from 325% to 150%.

Luna
-Purchasing Eye of Skadi on Luna will cause Lucent Beam to grant her a buff that lasts for 12 seconds, and gives her 10% movement speed and 30 attack speed. Beams from Eclipse will not grant this buff.

Broodmother
-Purchasing Manta Style on Broodmother will decrease the AoE damage she and her spiders take by 25%.

Skywrath Mage
-Purchasing Aether Lens on Skywrath Mage will now cause all his single-target spells to also hit the target of his Ancient Seal.

All I've got for now, but add more if you want I guess. This thread is more to discuss the possibility and the impact of changes like this being brought into effect.

This sounds like an interesting idea but it would make make balancing a nightmare and the game even more complex (although I wouldn't mind the complexity part).

This is just dictating itembuilds for heroes and it makes no sense at least in examples you provided. I'd pick BKB on TB in any game then, even when I am facing 5 rightclickers just because this would be the best lategame survivability item for him regardless of the enemy team lineup.

Well...of course the interactions would need to be a bit weaker than this or the item would be an item you wouldn't really want on the hero.
But it wouldn't dictate items. Or would you buy Mkb for true sight in any game?
Exactly these mechanics would be interesting. How about instead of the illusion damage reduction Terrorblade's trail of flames damages enemies that walk over them?
I don't like the idea of "boring" +10dmg effects or something but unique effects sound pretty interesting.

I'd buy an MKB for PA almost every game anyway with that much evasion from items. True Sight makes Glimmer Cape obsolete against her so, yes, if MKB got this addition I'd buy it every game.

Firstly, it'll be kind of a nightmare for the devs. I mean then they'll have to chode the interactions of each hero with each item separately. Also, as michi said, balancing'll be an issue.

I feel like this would just lock in item builds, and people are already so stiff with their builds. I wanna see variety galore. Seeing everyone build the same items on heroes over and over and over is awful. I like to spice up my builds. Juggernaut with Aether Lens / Solar Crest / Moon Stone / Daedalus. Why not?