I had three rabbits at one point. Two were together, but one of them got along with either of the other two, so I could move that one in with Gus on occassion when I needed to. All three of them would have bunny parties in the back yard and did fine with a lot of room to hop around. I think it’s a nice change of pace for a rabbit if it works. I am thinking that Bun Bun won’t be a good boy, though, if he’s not neutered, but if you’re right there anyway, I don’t see what the harm would be to try, but don’t use me as the final word. Trying to bond 3 got nasty and I was afraid to ever try again. Noone beats up on Gus!!
I also don’t recommend you neuter him simply for the occasional play date if you aren’t having any other problems with him to warrent surgery. Are you sure he’s not neutered? I got a rabbit from someone who called herself a breeder, who’d gotten a rabbit from someone else. She was selling him because he wasn’t interested in the girls. We figured out why!!