Shoot, I did that a year ago. However, unlike being half-alien (or half fae), Plantsimism isn't genetic, so you can't exactly spawn a nature fae just by breeding. By turning a changeling into a plantsim and making them spawn a plantbaby, yes.

Making your own is a little tricky, but it works exactly the same for a multiple ideal plantsim mod as for a multiple pollination technician mod-- and you can learn how to do that by reading Simgaroop's tutorial.