Safe birds to keep with Chinese Quail?

I have a -large- cage that I have a couple of quail in the bottom of, but because it's so big, I'd like to be able to keep another bird species in there. I'm aware that most parrots, parakeets, etc, are out of the question, but I wondered what my options actually were? I assume Parrotlets (celestial) are also fairly aggressive and unsuitable?

I am aware they can mix with canaries and some finches, but I don't particularly want finches or canaries as we already have a couple elsewhere. I was wondering if Diamond Doves would be alright?

In regards to what I could offer the birds, food and toys, etc, can be bought if any need anything. As I said, the cage is large, I'd like to get a pair of whatever I'm having. If they're friendly or flying breeds, then I'm in most of the day and can close the room to allow them out for a flight or explore. I do really like friendly birds and if there were any suitable, I'd prefer ones that I could interact with.

Thanks for any help!