This may not apply directly to your question, and more to druids in general, but in the past week or so Jeremy Crawford clarified on Twitter that a druid can ready a spell, shapeshift, and then deliver the spell while in animal form. So while you cannot cast a spell in animal form, you can complete a readied spell. It would be so amusing to see a druid shapeshift, charge at the enemy, and release an attack spell part way there. I would definitely give advantage on that charge attack due to the shock the enemies might be in on having that happen. Think about a druid/any caster multiclass that has fireball or lightning bolt. Ready the spell, shift, charge, and release a fireball or bolt at the enemy that looks like it is coming right out of your mouth. Or even just multiple magic missiles, for a lower level spell. lol