I'll concede the +1/+1 theme, but even that is pretty loose (there are way better options for supporting that theme).
But I don't see why having lots of morphs is "synergistic" (whisperwood being one of the very few exceptions). Morph to me really isn't a "theme" in the sense of how we generally talk about themes (like +1/+1 counters, enchantress or whatever). Having a bunch of them adds to the mystery, sure, but doesn't really change how they play. Now, if we had more morphs that you could penalize people for targeting, maybe that would change things. But as it stands, running marginal cards to hit a specific morph count makes little sense to me.