I would like to see a "don't train" option for players who have currently very high skills and whose managers don't want to see them improve more - and consequently rise their wages - but want them playing in the positions they are supposed to.
I am currently training PGs and I think my training is complete, I've already achieved my goal of having 2 world class guards in my roster, with a nice backup for them. Continuing to train PGs would mean having to sell one of my great players and downgrade my perimeter. I could switch to C training, but this means that I would be forced to sell one of my great centers, because they currently have $200k of wages on aggregate, and if I keep training them because of my younger trainees they would soon reach more than $300k. The solution could be training SF, but it wouldn't fix the problem, since when I train my SF on the paint my Cs would receive training and their wages would rise, the same for my PGs.
I think BB is reaching a point (at least for teams that are playing for almost 10 seasons) where training is getting meaningless, because if you have too good players there is no sense in training them more due to high wages, and training young talents of 18-19y/o means making your team weaker. I could start doing like B3 finalist Vitoria Devils and just train game shape and live with my gate receipts and cup prizes, but I don't want to, since for me training is the most important thing on this game, or at least it should be.
So I think that a "don't train" option could be a nice solution for this problem, it could allow stronger teams to keep their superplayers and also train younger talents. Of course, keeping a "don't train" superplayer playing in the position that is being trained means that the team will lose one of the training slots available, but that could be the burden to bear in exchange for this possibility.