I think the ideal training system would be where everyone can very slowly improve (except for the old guys) and you can set individual training for a few, chosen guys of your choice, in any skill you want. Some players would still train faster than others, like bigs in rebounding or smalls in handling. Take out the need to play players in particular positions, as it's completely unnecessary, or maybe it could give a very, very slight boost, which would be realistic. GS would still be affected by how many minutes your guys play.
Take out the scrimmage and have another league game per week, or make it so that the scrimmage gives you a small amount of attendance money. (That idea is purely to make it so that managers stay online longer which is, in my opinion, a big reason for the current training system.)