This is my off-the-top-off-my-head lightweight lens alternative

accessors.hs

-- Data decls could be in their own module for qualified import?
-- Alternatively, there might be a solution in GHC 8's duplicate record fields...

-- Only thing to update to add fields is the accessor functions

-- Test with an int and a str
data Test = MkTest Integer String deriving (Eq,Show)

number :: Access Integer Test
number f (MkTest n s) = (f n, MkTest (f n) s)

str :: Access String Test
str f (MkTest n s) = (f s, MkTest n (f s))

-- Kitten with a name, an age and a list of favorite words
-- Example: grab name (Kitten "Techy" 5 ["Meow","Mew"]) == "Techy"
-- Example: change age succ (Kitten "Techy" 5 ["Meow","Mew"]) == Kitten "Techy" 6 ["Meow","Mew"]
data Kitten = Kitten String Integer [String] deriving (Eq,Show)

name :: Access String Kitten
name f (Kitten n a w) = (f n, Kitten (f n) a w)

age :: Access Integer Kitten
age f (Kitten n a w) = (f a, Kitten n (f a) w)

favWords :: Access [String] Kitten
favWords f (Kitten n a w) = (f w, Kitten n a (f w))

-- In library
type Access a b = (a -> a) -> b -> (a, b)

grabf :: Access a b -> (a -> c) -> b -> c
grabf a f m = f $ grab a m

grab :: Access a b -> b -> a
grab a m = fst $ a id m

change :: Access a b -> (a -> a) -> b -> b
change a f m = snd $ a f m