If you talk about Vueling you have to be careful,
Crossair took over Swissair´s assets and almost ended up in the dustbin itself. Swiss rose from the ashes of the combined airlines to be taken over by Lufthansa (even though BA fluffed its chance of a takeover before that).
Vueling is based at Barcelona, which should be emphasised is not an Iberia Hub. Iberia should mold itself to the successful Vueling and not the other way round. As they say “if it ain´t broke ,don´t fix it” .
Iberia Express and AirNostrum-Iberia Regional do a good job of feed into Barajas. Keep it that way.
BA could actually learn from these for its own feeds. It treats Flybe in a very offhand manner which does not do it any service. Sun-Air (BA´s franchise in Billund) does little to nothing for BA – it should be demanded to provide better feed or lose its franchise. In fact, BA could design a much better strategy with its franchisees and codeshare partners to increase its feed from them – however, that might demand too much new thinking for BA´s own capabilities.