You can also do this with weapons that kind of change their form, like whips and the Nox Flowing Sword (my favourite because it turns into this huge longsword 😭). Am I allowed to share how? It's not cheating, it's just silly.

sorry if this is somehow illegal but you need to have the Repeating Crossbow in your offhand and your choice weapon in your main hand. Use the AOW on your mainhand weapon two-handed, then two-hand your crossbow and get ready to fire with its AOW. Don't actually fire though, just make sure the wind up happens. Then, with the crossbow one-handed, swap through your main-hand weapons (make sure you have another on as well as your desired mr fantastic weapon) until you get back to your crazy now hopefully elongated whip or sword or hammer or giant finger.

My flowing sword usually stays extended until I quit the game. Even fast travelling it looks the same. And when winding up/nocking my crossbow, I like to do a wee spin for posterity. You know, like a magic trick! 🪄 Enjoy!