The first thing that bothers me is that stamina is declining through time, wheter it be a 18 y.o. or a 38 y.o. veteran. This is unrealistic! IRL your stamina doesn't decline over time if you train (anything) or if you play games. The reality is quite the opposite - it improves!
Honestly I kinda share the same sentiment. How do draft players (can you imagine) have good basketball skills and 1 stamina? Imagine having go through organized basketball (and have the best skills in the draft class) while having atrocious stamina. How is that even possible?
Frankly speaking, I think instead of having the training court boost free throws, they should scrap it totally and replace it with stamina training. In reality, we haver a hall of famers who are bad in free throws (Shaq is one), and a handful of other current NBA players (Jakob Poeltl, Dwight Howard) who are bad in free throws as well. In fact, Dwight Howard claims he hits all his free throws in practice and suggests that it is more of a mental strength thing which can't really be solved by just shooting more free throws in training. But have you even seen any young NBA or G League player (or even NCAA player) who starts panting after a couple of runs?
In fact, manager games like Hattrick (whom I've always seen as the sister-game of BB since a lot of us joined BB thanks to the ads on Hattrick back in season 3) have made stamina something which is trained passively. Iirc you can select much many % you would like to train and it kinda affects your players game shape or something, can't remember too well because it's been years since I last played.
To make things worse, the new game engine has a bigger effect on stamina. Although it's meant to combat undersized rosters, but it heavily affects youth training, especially when the system made it possible to generate illogically low stamina players.
The third solution I have is that the players' stamina improves according to their minutes. I would say that stamina should only improve if the player hits 'golden minutes' (60-80) during the week and decline otherwise - much like game shape, but the stamina improvements would of course be smaller on weeekly basis and thus show themselves in the long run.
Honestly speaking, I dig this suggestion. This should actually be the best fit, as stamina training would most probably encourage undersized rosters even more (well, not that they training anything other than game shape and stamina I guess), so this should be the best solution which won't benefit undersized squads too much. If we replaced free throws bumps with stamina bumps in the training court, it might just encourage people to have less players, since they can have bonus stamina training anyway.
Another one I'd like to see implemented is a floor for stamina on draftees. Make it awful or inept at least. Atrocious and pitiful seems a bit too silly. This would go well with the golden minutes feature, as if you don't train your trainee within the golden minutes (eg maximize training for 48 minutes per week), it can still drop as usual, hence there will still be incentives for stamina training.