For most of the last two seasons I did "whole team" training in those disciplines where it is possible. I started with a whole squad of young players, and I was getting significant numbers of pops - at least two or three every week, and sometimes, when training 1v1, for instance, up to ten pops across my twelve or thirteen players. I think that, overall, is a faster improvement to my team than I would have got by concentrating on half the team, and then selling some of them to buy new players to populate the other positions.
Training the whole team is not the 'majority view' on BB, and it certainly doesn't help in creating one-dimensional monsters to sell on the transfer market. But I want rounded players, and I want a 'whole team' approach to games - where my bench players are not much worse than my starters, and no-one earns a fortune.
Such an approach can't work for everything - you can't train the whole team on ID or OD, for instance, so it relies upon you having players with some skill already in the 'untrainable' skills. My team is a lot better than it was two seasons ago, when I first started, and I'm hopeful this year of some actual success on the court.
All this is to say, don't rule out the whole team training. It is an option. And it can work.