Of course, mergers among banks and savings banks must not be a taboo topic - but, by the same token, they must not be a regulatory objective, either. I admit to being a fan and proponent of diversity in terms of bank size and business model, as this makes our banking system more stable.
Supervisors are not supposed to be making structural policy; rather, they ought to be actively working towards proportionality in regulation. This is precisely why banking regulation and banking supervision are already designed with a large degree of proportionality.