This is a great post with a lot of Great information.
I have spent many $$$ attempting to get DD more speed with some of the BEST speed and strength trainers in the country.
They ALL have helped her gain a little edge using what she has in order to get a little quicker however;the BEST advice we were given was this. You cannot teach speed! You can improve what you have...
Remember; Sport Specific Training... If you want to be a track star run, run, run,
If you want to play softball learn how to hit,field and throw... It does not do you any good to be a runner if you cannot do the others...
As far as the comments with HS training...Yes, not a lot of supervision with weight lifting and in some cases it can be dangerous having upperclassmen supervising lifting activities for underclassmen.
I know the advantages of strenghth training as it relates to hitting and throwing but, training and teaching the play of the game including fielding and physical play must be a part as well if you want the player to rise to the top.