You could do it and it would be stronger and come up faster. You'd have to reduce it to a small amount of liquid though. Actually would work better to fully extract and then re-dissolve in a much smaller volume of liquid. When the liquid goes too far up it will still absorb but not as well, which is why just a few mLs of liquid works best for plugging.
But yeah, rectal BA is definitely higher for mescaline. Should be around twice as potent. I actually plugged cactus extract once by doing what I described above. I had some dark brown chunky powder and dissolved it in a few mLs of water and plugged. It was a good ROA.