A more standard broom mount would be cool! And as you noted, in a similar vein to Harry Potter, they could do a variety of different types, styles, themes regarding brooms so there's plenty of room there to explore (similar to what they've done for horses, some wolves, etc.).

Can't speak to the whole spider mount thing... Personally, I hate spiders with an undying, burning passion. I'm not afraid of them, I legit HATE them and want to kill literally every one I see (it's a thing, been bit a LOT in my life, lol).