I fundamentally disagree with a bunch of your unlikelies. Given you run counterspell and remand, I can see why you wouldn't like miscalc; it's still perfectly fine, just there are better things.
Well, unlikely is not the same as impossible. I would put probably put a Miscalculation under the Scepter if the opportunity presented itself, but I wouldn't be really happy about it.
Furthermore, the problem with Scepter isn't that there aren't enough interesting 1-2 cmc instants, it's that you have to put them in your cube over potentially more interesting 1-2 cmc sorceries and 3+ cmc instants and sorceries, just to make Scepter a viable card. If you don't support it, it just becomes a mediocre inclusion in your cube, and at that point you might as well cut it. Thus it either warps the cube around it (which imho is undesirable) or it is a suboptimal card (which, again, is undesirable).
E: A weaker overall power level is not achieved by keeping the Scepter in your cube, it's achieved by making choices that don't subscribe to the power-max ideology. Like swapping out Lightning Bolt for
Rift Bolt (better for aggro, and synergy with bloodthirst), or Swords to Plowshares for
Oppressive Rays (a one-mana removal spell that favors aggro decks, and synergy with an enchantment matters theme).