As to your first point about relics, I would be careful in a couple of areas.
The Eucharist is far more than a Material Object. The Eucharist is a Person: Jesus Christ and while I get your point, we don't want to use sacramentals which are points of contact for our faith, like holy water, handkerchiefs, etc. We may wind up causing more confusion.
Also, as it relates to the Genesis account of the Tree of Knowledge of Good and Evil, that's not a great example, as the Church has historically understood much of the creation account as allegory, steeped in deep meaty theological revelation, more apparent in the original Hebrew.
Although many fundamentalists will take it as literal tree, you would be hard pressed to find a Catholic scholar, (and I'm not just talking about the more modern ones, I'm talking about Augustine and Jerome), that didn't say that portion of Genesis was symbolic language.
Now there are good examples to use such as when the dead man was tossed into the same grave where the bone of Elisha were and was immediately raised from the dead. (2 Kings 13:21)
In Acts, we see that shadows of the Apostles were points of contact for people's faith and so forth but again these are making arguments for relics and sacramentals.
While the principle is similar, we diminish the Eucharist when we use them as an example.