To avoid those endless discussions with @yindesu (no harm intended but it’s always like — DO NOT USE — But it’s printed on the release — No, do not use because this that — etc. and I am not saying who is right or wrong) we really need to detach labels from catalogue numbers systematically.
So all points of view will be OK. People wanting to see the catalogue number in this label will see it, people wanting to see the catalogue number in that label will see it as well. 
I think what @yindesu meant to say is maybe:
Someone said such letters should be associated to the holding companies, not to the label.
This association works for some time, e.g. for imprints of JVC Kenwood Victor Entertainment Corporation (the holding company of Victor and SPEEDSTAR), but that doesn’t hold for all time.
The major example are Ki/oon and Epic Records, both are now imprints of Sony Music Labels Inc. but use the distinct catalog letters KS and ES.
I think the point was that it should be associated with whichever entity they’re associated with. In the case of VI that’s Victor Music Industries / Victor Entertainment / JVC Kenwood Victor Entertainment. In the case of KS it’s “Ki/oon Music” (which happens to be a subsidiary – not just an imprint-- of Sony Music) and for ES it’s Epic/Sony (also a subsidiary, not just an imprint).
There was talk of doing pretty much exactly this at one point. It was probably on IRC and not sure if it ever manifested in a proper ticket or what not, but it sounds like the best solution going forward to me.
It was at the summit, and I’m pretty sure there’s a set of tickets (STYLE and MBS) for this.
That would be nice, but doing such correct arrangement poses many design/technical issues and maybe have trouble with exceptional minor labels. IMO, at least meanwhile, just linking catalog numbers to the list of imprints would be helpful.
The information about holding company or distributor can be obtained from relationships between labels.