Look up 4 week integration techniques by aart? They wrote a great piece on integrating chicks at a younger point so that the flock won't see them as much of a threat.
As for my experience, last summer I had 2 full sized hens and a turkey. I did 2 weeks of see no touch with a few days of {short} Co foregoing with a subflock of new to me bantams {1 cockerel and 2 pullets, 12-14 weeks old by my guess}. They integrated successfully, albeit with a bit of pecking order scuffle. Blood was only drawn once, and now they are happily co existing with the larger flock mates.
Now I have 4 Buff orpington chicks who I will be integrating at 3- 4 weeks. They are 2.5 weeks now and I am doing very short co-foreging field trips and have a see no touch wire brooder set up in the run. Yesterday the bantams checked them out and there was a tiny bit of pecking, but more to see 'what the heck are these things and what do they do,?' then to be mean.
So if you have the time/energy/set up, bantams can absolutely be integrated within a larger flock. It will take time. It will take watching over and seeing if you have a bully that you may have to separate for a day or so.
