So, a few points:
Spiritual has 1 more permanent "removal", it's rejuv. It has a huge side effect though. Also you can remove weapons and shields with "Give", which bypasses immaterial as well.
Also, this is way stronger than Earthquake, because as currently intended, it's both a removal or just pillar destruction. However, as currently Regrade goes, you need to ask serprex if normal permanents actually counts as stack of 1 (I guess, no).
On the quanta denial alone, I'm not even sure if it's actually worse than EQ. Having something always take 1 stack of the pillars (essentially, per draw you do) means you are never able to get over an amount of quanta per turn, unless you hold the pillars till all of your pillars are gone. This can have great synergy with Pests, who only can sustain you down by a stable amount of quanta. Also, it's way cheaper to get more out of it, it's just slower.
For this reason, I think making it stack is actually less of an issue, as letting the stack go destroyed is the optimal counter, unless you can go over it. Also, I like stacking it, because Demigods draw by 2, so unless it can go up to 2, it's even less useful against them.
However, the major difference is that it requires very little
and goes along with spiritual, where Sabbath is. Also, it's a PC along with that.