We didn't do this, but we did talk to two DJs that offered both. Like a guitar accompanying the song you walk down the aisle to, etc. It was obviously more expensive that way and wasn't what we were looking for, but that may be worth looking into. I assume some DJs/bands wouldn't want to work together if they hadn't prior.
My cousin had this at his wedding. He plays trombone and members of the band he played with at the time played for some of the time and then a DJ did the rest. It worked out fine. It was nice having a mix of music styles.
My dad is a wedding DJ and he has done weddings where the entire ceremony or just the bridal walk was done by a band and the reception was done by him. It is not a problem but make sure your DJ has done this before; everything will run a lot more smoothly
We didn’t have a DJ but we had an audio tech who played our background music for 30 minutes, a band who played for an hour, a Frank Sinatra impersonator who sang for an hour with tracks, then the band when back on for 90 minutes. Really fun having the different types of music!