Ok, slight thread drift..
At companies where Meritorious promotion occurs prospective candidates have been typically identified by the C&T establishment well in advance. It would be 'ethical' to have a promotions committee to oversee the process so as to keep the process transparent and fair. A promotions committee would/should comprise the CP, head of C&T, some check captains, training captains and line captains also a representative of the pilots union (preferably a captain so as to prevent any 'deals' being made).
It is difficult for a management to be 100% ethical, all of the time. High ethics should, of course, be an overiding priority. This should be understood. The application of datal seniority does have as a redeming feature a reduction of personal bias. However, the selection of a candidate for any position is an intrinsically subjective and discriminatory process.
Despite the seeming objectivity of datal seniority, I am aware of instances in absolutely strict seniority companies where Managment has manipulatued the process to acheive an outcome which subverted the so-called 'protection' of datal seniority. Defamation laws prevent me from giving specific details.
As some other posters have pointed out, the topic is a very emotional one. Despite ones person preference towards either system, it is valueable to at least discuss the various options - if only to re-inforce our own preference!