[NoOne]

if you want to hand-tailor each team with specific players from different teams and different eras, it will require effort.

what micro said is probably the best way to go, but you'd need to know how to setup the files and such, which you'd have to learn on your own through existing threads in the forums and mimicing existing "../data/stats/" files. then import historical players in game as you normally would, but select your customized file instead of one of the default ones.

either way, if you want somethign that custom and not random, you'd have to setup each team with each player you wanted.

you can do a random debut leauge or specific year imported teams from history of any combination by selecting them from a list during game creation process... or afterward using import historical player option in game.

screenshot shows menu after selecting import historical players in a game (free agent list) then you see an option to select a custom file and it even tells you the format required of that file) it's from ootp18, but will look similar in 19.