Random Generator gave me Healing Salve and Wall of Air. My first thought was "Good. A very easy card. I'll just make a wall of air that gains you 3 life when it comes into play, and make another card." Then I made that card, and stepped back. It didn't seem right. That card would have made sense if I got Soothing Balm, but Healing Salve is a modular card, and it kind of felt wrong to not make the mashup modular.

So I buckled, made something a little more confusing, and in the process ended up with another uncommon. This time, it's not uncommon because of confusion issues, but because modular cards create too many options and shouldn't be at common that often. sigh. On the plus side, I think I like the card...

I'd be happy with the simpler version. You've kept only minor parts of one half of a mashup before.

I think an "enter the battlefield" trigger would be sufficiently mash-up-y, but I agree the prevent-or-token is better. In fact, I think it could maybe be common, if you're stretching for commons -- a flash-wall is potentially confusing, but it's not worse than Village Bell-Ringer?

The oddest things for me is that it can't prevent damage to a player (eg. from a spell), and that it introduces a new token type, but both of these are small things, and I think it's probably correct to leave it as-is.