Hunter's Potion + Monster Hunter
Quite simply, I think the Monster Hunter passive should be added to Hunter's Potion.
This might mean that Hunter's Potion can only be purchased if you have Smite, but I don't think many, if any, champions purchase Hunter's Potion if they are not jungling anyways, so doesn't seem like much of a loss.
The reason I think this would be a good change has mostly to do with one champion, Ivern, however it is possible that other champions may chose this route as well.
Hunter's Machete and Hunter's Talisman are useless on Ivern, with the exception of the bonus exp gained from Monster Hunter. This already decreases the gold efficiency for Ivern to purchase either of these items, but it is still essential in order to stay up in levels. Continuing to build any jungling item is still not ideal for Ivern because he can gain better gold efficiency from other items in the game.
Along the same lines of what I said earlier, most champions that take Hunter's Potion are junglers, and therefore they are also likely to build a jungle item. Starting with Hunter's Machete gives better damage output, improving clear speeds. Hunter's Talisman is generally the better sustain option. Hunter's Potion is also a sustain item, but it does not build into anything, so champions who still plan on completing a jungle item are still more likely to start with Hunter's Talisman over Hunter's Potion. This means they would gain no additional benefit from buying Hunter's Potion from this change.
However, I have noticed that some champions currently don't even complete their jungle item. This would possibly be a good option for that strategy.