How to incorporate my brother in my wedding!!

I like the idea of them co-officiating. Your BIL can do all the legal stuff, but your brother can also add to the ceremony. This is done commonly in inter-faith weddings and you can probably find some outlines online for this too. Your brother gets the same attention and importance as your BIL.

Edit: example-- I think it would be really cute if your brother introduced your fiances vows as though your FH is not only promising these things to you, he's also promising your family. Your BIL can announce your vows. Your brother can ask your FH if he takes you to be his wife, and vice versa.

I think a reading is a really nice idea! Or he can be the games keeper and announce some kind of couple game during the reception? I know some people do the shoe game, which is just involving you two. Or, for example, this will be announced by our DJ but we're going to give everyone a "how well do you know the couple" quiz to fill out at their seat, and then sometime during dinner we'll do a "keep your hands up if you guessed right..." and whoever wins gets a bottle of prosecco! It'll be fun since people are from different stages in our story and most won't know every answer! Maybe your brother could be in charge of that?

One of my brothers is going to play the song for our walks down the aisle, which I'm really excited about since he's been musical his whole life and it's a really big part of our childhood. It's going to be a song that's really recognizable "Stay With Me" by Sam Smith, which I know isn't technically romantic if you listen closely but my fiancé was OBSESSED with Sam Smith when we first got together when we lived in London so I think he'll get really excited to hear it as a surprise. And the tune is quite sentimental!