Mages should be having mana scalings

These days there are a lot fo talk on mage/ap assasin itemization, and how lackluster does it feel, with only a few viable but mandatory items to choose from, and how ap items dont have any depth, making them unsatisfying. For a big example:
In my opinion one of the problems of the ap itemization is that it doesnt really make a difference between mage and assasin items. They build the same thing, eventough the 2 classes have a lot of differences. I think a really good solution to this would be to, make magic pen items a better choise on assasins and worse on mages. You know, kinda like lethality with ad assasins. They are the class that its the most viable on, but sometimes(well mostly when its broken) its built by other classes like adc's. But then, mages would lose alot of dmg right? Afterall magic pen is is a pretty important thing on them, right? And this is where mana scalings come in. Currently in the game we have four champions that are having some kind of mana scalings according to the wiki. Tbh i was kinda surprised by this number, i honestly tought that there were a few more. So, as we all know mana items are not really viable right now exept for ofc and maybe on battle mages and/or tanks. So, my idea is that some mages should get mana scalings on abilites. This would compensate for the magic pen items getting moved to assasins instead. And overall it would make building mana more worth and satisfying. It would open up a whole new level of balancing items and champions. Want some dcr and dmg? Want to be a bit tougher to kill? Want more mid/late game dmg? . I think the best champions to give mana scaling to are the ones who should be good with / beacuse its easy for them to stack it, but since it lacks viability they are not even thinking about building it. Or just the ones that are building it right now. (well mabye it would be a stupid idea to give more scalings to him) These are my quick tought on this, and im really interested on your opinions on this too!