Most things in life require some sort of trade-off. We may not approve of the choice in question and therefore not make it, but there’s often no way to do things “for free”.
This is no different. But it seems to me that the OP is asking for that, asking for a change in things to make achieving maximum renown in a delve more convenient for him because the current options don’t satisfy that. That he doesn’t have the ability to devote the necessary time and effort on a Tuesday, and that he doesn’t wish to spend the time and effort (and resources) to build up a hoard to a level sufficient to conquer the delve with a faction-only team at level 500.
A high kingdom hoard is the rough equivalent of a low kingdom hoard plus those Potions of Power that the OP desires. It’s not an easy thing to accomplish, but it can be done with some level of effort. And it probably requires that effort to be a little bit every day for an extended period of time.
Now a couple of other related thoughts:
Potions of Power aren’t a cheap thing in Events. In addition to having to purchase every previous shop tier, that last tier including the Potion of Power (plus some other stuff) is 500 gems. But they only apply to that specific event and only for the remaining duration of that event.
If the developers were to be entertaining the idea of Potions of Power to be a more persistent thing, what would be a fair price point for that? Not just for the benefits of the potion itself, but a reasonable premium to account for skipping the steps that upgrade a hoard, but also the time and resources that would be saved by not having to take those intermediate steps?
Also, it’s my opinion that the fears about the need for 2500 renown in a faction for kingdom power levels is overblown. At least right now. Because the spoiler sites suggest that this isn’t a need until Power Level 29 which no kingdom is near right now. Moreover, there’s no reason to believe given the current state of the game that any kingdom is going to get to that point anytime soon. The two highest kingdoms are at 25, they’ve both been the focus kingdom of a Campaign – meaning they’ve gotten a Tarot troop, a campaign mythic/boss troop (and often in multiples) – they both have their delves, et cetera. And with there being 34 kingdoms and at least one more in the pipeline, chances are that they’re only scheduled for 1-3 new troops per year.
Not everything is meant to be easy. Or to be something that can be circumvented by some sort of “EZ” button. Some things are meant to take time and effort, often time and sustained effort, and it’s each individual’s choice as to whether or not they wish to put in what is necessary.
And if one doesn’t wish to put that in, sometimes one just has to accept that it will remain un-done.