Lack of Build Diversity and How to Fix It

I could go in to detail on why any other solution has failed, however this thread would then take an hour to read and no one would read it, so I'll just go in to my suggestion.

We have no choice of slot efficiency VERSUS gold efficiency. Any slot efficient item is also gold efficient (including value in that situation of the item's passive and active abilities). So there is never a real decision to be made, it is always an analysis of what the best item to buy at the time is and then buy that item.

Consider, in contrast, if there existed items that were SLOT efficient but NOT GOLD efficient. Of course, you would never see these items purchased early game, but they would make a huge difference late game. Imagine, if you're an ADC and you've built IE>Bers.Greaves>PD>LW>GA and are about to purchase your final item, a BT. Now imagine, if neither team has taken a single inhibitor turret yet, and if you had the option of instead of buying BT you could spend an additional 300g and buy BT2 which had exactly the same stats. Why would you buy BT2? Because it can be upgraded for 1700g to add the effects of a Bilgewater cutlass (and then maybe again to upgrade that bonus to BotRK stats). So now you have a choice, do you buy the BT to be gold efficient or BT2 to be slot efficient?

Of course I'm not saying to make exact copies of items that cost a bit more and have the option to be further upgraded for gold inefficient amounts, what I'm saying is to make new items that are the best use for a slot but are NOT the best use of your gold. So early game you obviously buy gold efficient items, but mid and late game you need to evaluate how long the game will go and whether it's worthwhile to pursue some slot-efficient items that aren't gold efficient.

Few enough games last super long, so perhaps I'm mistaken in thinking this would add diversity. I just know that I've had games where I'm fed but can't carry fast enough (because someone quit or because the other team is overall just much better than my teammates) and I run out of things to buy even fairly early. These options would potentially add variety. The gold inefficient + slot efficient items could even have super-powered actives and such because they cost so much gold that you make a big risk in saving to buy them.

Thoughts?