Mashed potatoes, instant potatoes, a couple of tablespoons of oil/fat . . .
These will a do the trick.
The real secret though for light, fluffy bread that will keep for days seems to be (for me) a low-yeast, long, cool rise. Try setting your bread up in the morning or night before you wish to cook it. Use 1/4 the amount of yeast and let it rise in a cool place or let it rise in the fridge.
The fridge works especially well with sweet dough recipes; controls the action of the yeast, keeps the dough sweet and makes a soft fluffy bread/roll.