To me, the purpose of an item is to offer choice to the player, giving them one set of bonuses out of many potential others, which the player has to select based on their intended strategy and playstyle. In this respect, Viktor's Hex Core does not fulfil the purpose of an item, because there is no choice as to whether or not it can be equipped. There is some element of choice in when to upgrade the item, but at the end of the day it's just a way of tying gold to Viktor's augments via a stat stick and an item slot.
Because of this, I would support looking into a different way to implement Viktor's augments. I know the OP is a big fan of quests, and I think a quest mechanic could be an excellent method of unlocking Viktor's augments over the course of a match. In fact, it would likely be much more thematically appropriate to Viktor than gold, because at the end of the day Viktor is a scientist obsessed with research, optimization and adaptation, not material wealth. Implementing the Glorious Evolution in a manner that encouraged the player to research, adapt or otherwise evolve their gameplay over the course of a match via a quest, rather than just dishing out upgrades alongside a gold fee, could go a long way towards letting players embody Viktor's fantasy, and so in a manner that would avoid limiting his diversity of itemization relative to other champions (which itself is antithetical to his character, as he strives to unlock the potential of people via the gift of technology).