I think you are overestimating the amount of influence cross-training will have on a player's skills. It has been suggested through math that the increase in cross-trained skills will be small- between .03 and .07. If you train an 18 year old center for six years , 2 years each in IS, ID, and REB, you will still have a triple prodigious C, with crap skills everywhere else.
Once I scored a basket that still makes me laugh.