For a vegan option, omit the egg and add extra oats to bind the burger together.
For more texture, if you're catering for adults or less fussy eaters, you can pulse the chickpeas, oats, and tahini, then mix in the softened vegetables into the chickpeas for a more textured burger.
To get ahead, make the mixture and store it in the fridge until needed, ideally no more than 4 hours.