Interesting idea. Seems pretty good to me. It does not only look arrow-like, but also similar to the lollipop (⊸).

Let’s try it out:

fmap :: Functor f => (a -+ b) -> f a -+ f b

Yes, this looks quite nice. Let’s compare it to the Unicode version:

fmap ∷ Functor f ⇒ (a ⊸ b) → (f a ⊸ f b)

They look similar indeed. 😉