One thing to bear in mind when you start making suggestions for additional Upgrades, alternate abilities or brand new "perks" which modify other things is that all of that stuff, while it may sound cool and awesome to use, has an effect on game balance and some new alternate abilities might sound really cool but might wind up being not-so-great in practice when they get properly balanced.
Just as an example, Arcane Lotus, which was released not to long ago sounds great as an idea; since Rose has the damaging Arcane Enigma ability why not give an alternate ability which heals? I like that as an idea and I was excited to try it out, but I quickly learned that it wasn't as valuable to me as the original ability or even as handy as it sounded in theory.
At the time Arcane Lotus was introduced I had given up on using Arcane Enigma as an offensive ability and instead relied upon it as an escape option to retreat. While I might use it's attack to vanquish spawns of Browncoats the low damage couldn't be counted on to save you in a dicey situation in Multiplayer or with any of the beefier AI Zombie Heroes or Bosses.
So the idea of having a version of that ability which would allow me to escape from bad situations and which would have the side benefit of healing team mates was immediately appealing and I jumped straight in to trying it out.
It was quickly made obvious that the Lotus ability was useless as an escape option because Rose receives a movement penalty when using it and it does not last for an equal amount of time; not only could you not travel far enough or fast enough to get away from a threat but you couldn't even manage to keep pace or catch up with team mates who might need healing. To make matters worse the ability described as transforming Rose into a "Being of pure Healing Energy" can't manage to heal Rose herself- the one factor which would make the movement penalty and shorter time limit truly worthwhile.
I really wanted this to be an ability which I embraced wholeheartedly because the concept was really sound but instead I never use Arcane Lotus in Multiplayer because the ability is to limited in actual usefulness and by taking up my very useful Arcane Enigma escape option it's actually a detriment. Instead I use it only occasionally in Garden Ops when the team has no Sunflower and I want to contribute as a Healer without being a Sunflower or using my Heal Flower Pots.
You make a good point on the balancing issue, but I dream of a PvZ Garden Warfare where our characters are fully customizeable. Since we can't change pants and shirts yet I suppose we'd be pretty far off from having morphable abilities.
