I don't think that is necessary. While there is a power difference between Sol Ring and Eternal Witness, it's not like there is a massive abundance of cards in that category that separating them out makes a lot of sense.
Ok then maybe
4 - Staple - Cards with enough base power that your cube is less powerful from their omission. They are cards that are likely to never rotate out of your cube unless you ban them for being too good. 3 - Strong - These cards are among the top cards at providing an important effect and/or supporting a popular archetype. 2.5 - Inbetweener - Not as good as a 3, but definitely better than a 3. 2 - Playable - These are fine cards, but they are either interchangeable (e.g. lots of removal, aggressive red 2-drops) or are build-around cards that need a little support to be good (Favorable Winds). 1 - Niche - These cards aren't usually considered great, but might be included to support some obscure archetypes, specific interactions, or if going deep on a particular type of deck / archetype / effect. No reason to cube - There isn't a reason to cube these over options. You might find some perfectly 'playable' cards here, but there is little reason to put them into your cube in the first place unless you are intentionally depowering an effect.
Maybe we should expand this rating to be more accurate.
5 - Super Duper Good - This card is super duper good. 4 - Staple - Cards with enough base power that your cube is less powerful from their omission. They are cards that are likely to never rotate out of your cube unless you ban them for being too good. 3 - Strong - These cards are among the top cards at providing an important effect and/or supporting a popular archetype. 2 - Playable - These are fine cards, but they are either interchangeable (e.g. lots of removal, aggressive red 2-drops) or are build-around cards that need a little support to be good (Favorable Winds). 1 - Niche - These cards aren't usually considered great, but might be included to support some obscure archetypes, specific interactions, or if going deep on a particular type of deck / archetype / effect. No reason to cube - There isn't a reason to cube these over options. You might find some perfectly 'playable' cards here, but there is little reason to put them into your cube in the first place unless you are intentionally depowering an effect.
Quarry Colossus, same cmc, "harder to cast" is basically irrelevant. They probably come out to being almost the same size, with a higher ceiling on Phyrexian Ingester. QC has a better worse case scenario, being that there are no creatures on board. QC gets rid of something for probably 3-4 turns, whereas PI gets rid of it forever.
4 - Staple - Cards with enough base power that your cube is less powerful from their omission. They are cards that are likely to never rotate out of your cube unless you ban them for being too good.
3 - Strong - These cards are among the top cards at providing an important effect and/or supporting a popular archetype.
2.5 - Inbetweener - Not as good as a 3, but definitely better than a 3.
2 - Playable - These are fine cards, but they are either interchangeable (e.g. lots of removal, aggressive red 2-drops) or are build-around cards that need a little support to be good (Favorable Winds).
1 - Niche - These cards aren't usually considered great, but might be included to support some obscure archetypes, specific interactions, or if going deep on a particular type of deck / archetype / effect.
No reason to cube - There isn't a reason to cube these over options. You might find some perfectly 'playable' cards here, but there is little reason to put them into your cube in the first place unless you are intentionally depowering an effect.
5 - Super Duper Good - This card is super duper good.
4 - Staple - Cards with enough base power that your cube is less powerful from their omission. They are cards that are likely to never rotate out of your cube unless you ban them for being too good.
3 - Strong - These cards are among the top cards at providing an important effect and/or supporting a popular archetype.
2 - Playable - These are fine cards, but they are either interchangeable (e.g. lots of removal, aggressive red 2-drops) or are build-around cards that need a little support to be good (Favorable Winds).
1 - Niche - These cards aren't usually considered great, but might be included to support some obscure archetypes, specific interactions, or if going deep on a particular type of deck / archetype / effect.
No reason to cube - There isn't a reason to cube these over options. You might find some perfectly 'playable' cards here, but there is little reason to put them into your cube in the first place unless you are intentionally depowering an effect.
Or maybe Olivia's Bloodsworn is also a 2? hmm hmm hmm.
I think Corpsejack Menace is not worth a guild slot.
Especially since 9-11 of the usuals have Ulamog's Crusher, while 15-17 have Artisan of Kozilek, according to that average cube thread.
I think i'd still go for PI.
Saying it's a 7mana Nekrataal is inaccurate I think. He kills the thing, whereas QC just super-Oust's it.