This hive now has its inhabited feeder box at the top (completely full with a mix of brood comb and honey reserves), warre brood chamber with 5 of 8 comb drawn from top bars, and a second warre box below in case they need more space. They seem to be doing well on their own (obviously I can't feed them via the feeder box or above it). I accept to let them manage things on their own and move down into the warre in their own time, however long it takes them.
In retrospect, it would have been better to cut out the comb from the brood box and suspend it in frames as soon as the problem was discovered. At that time, I did not have sufficient kit or knowledge to manage that.
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Erichalfbee, Dani, thank you! Your advice was good. I should have listened!