Partly inspired by a Hearthstone card, Lightspawn, and also by M15's new "base stat" wordings... I'm not even sure if this works the way I expect it to.

i.e., with no counters, it's 2/2. With counters as prescribed, it's 6/4 (2 base + 2 counter toughness = 4 base + 2 counter power). Then what happens if you put a Giant Growth on it? I think it becomes 12/7, right? As opposed to 9/7. I might be overthinking it.

You have to apply characteristic-defining abilities before you even get to effects that set "base" power and toughness, so this ability doesn't work and it's no different than being an innate 2/2 with whatever counters and boosts you put on it.

Even if it was a 0/2 with "This gets +X/+0 where X is its toughness", you still don't get to take the counters into account by then, which defeats much of the purpose.

Yeah, this has problems similar to how the 5-power-matters cards in Naya did. Every Mosstodon is activated or triggered rather than static.

­Riptide Mangler is the way to do this. ": Change ~'s base power to its [current] toughness."

Thanks! Back to the drawing board, then...

Does it work if it's "0/2 gets +X/+0 where X is its toughness"?