This issue has been brought up several times in the past few years. When we talk about bibia being granthis in the Darbar Sahib, I always think, how many "other" gurdwara sahibs have their head granthis / main appointed keertani as bibia inside and outside of India? I have seen a few keertani jathas of bibia, seen bibia who do occasional keertan seva in local gurdwaras and also seen a bibi doing katha, but I haven't heard about many doing the seva as the main person in any gurdwara sahib. Before jumping onto the pavitar seva of Darbar Sahib, bibia first need to become active in other gurdwara sahibs.
And, it would look better if bibis were taking more interest in this topic. lol