If the guy has great skills and intelligence etc, and hes rating will increase as he plays more games, then his TALENT remains a natural part of him that can never change. Would a guy with 1.5* talent with huge other skills be the same as a 4.5* guy with very little other attributes accept con, etc.? Basically, should i go for large talent factor and forget the rest?

In the long run develop the high talented player. For the short gain, then a highly skilled player with low talent is better.