that's an EXTREMELY dangerous power, more so than our Shapeshifting.
Besides his new power Echo storm/memory (something echo anyway lol) there's much more that could be classified as Memory based... His regeneration seems to be largely influenced by his body returning to it's original state, he can change others but based on his memory (the people in jail, Laurie) and he can implement changes to his body based on memories he took from animals or monsters (gorilla arms, mantis claws, crocodile and spider armor, but his last 2 armors seem largely based on Valravn and whoever/whatever else he fought or just remembers. And lets not forget that scythe based on whatever monster memories MC got from digging around Deryl's body. He just had them after his evolution... Well, the scythe he made... )
It's really not a question if Memory would be stronger or Body... The sum of the two greatly exceeds either one on it's own...
I would not be surprised if the medium armor not only improves his Echo power but also weakens any mental attack on him..
Edit : The power to return an enemy to his mental state of his youth would be VERY powerful, The power to bring an enemy back to his psysical state of his youth would be too, but imagine being able to bring an enemy back to his mental and psysical state before turning superhuman? That would be epic.