It depends on the personalities of the large fowl hens. I have my bantams separate now, but that wasn't always the case.
If you do get another bird, it will be a happier bird with a buddy so that she isn't the only new one. Make sure you have adequate roost space, as the large fowl peck and peck at the bantams that get near them on the roost. If they have no escape, it can be bad.
If you only have one feeder, you might need another one as the large fowl might not let the bantams eat. Yes they are that mean to each other sometimes. If all goes well, you will see some pecking but no blood drawn and no feathers plucked out.
IF blood drawn or the bantams don't stand up for themselves at all, cower, and look as though they are about to be killed, you need to separate them pronto!
So I'd try it if you want bantams, but I'd get a pair. It is a good idea to quarantine for a month, and dust for mites/lice and repeat every 7 days until there are no bugs for newcomers. Some diseases can pass quarantine as they can be asymptomatic carriers, so your safest bet is to get chicks from a hatchery/feed store or reputable breeder and raise them separate from the others until they are old enough to integrate (usually around 4 months is good but you might be able to get by with it sooner).