dola,
i decided to give this a try. using a standard MLB lahman import (1974), i simmed a few years, then manually added toronto and seattle on the first day of pre-season (which is the only time you can alter league structure). there was a bit to do with the teams (logos, parks, assigning city, etc), after that i prepared for the draft itself.
this is where most of the details is the responsibility of the commish, since there are no facilities to setup a custom draft. whatever method you choose, you can assign a new team to a particular player through the editor tab in the player profile. for this expansion, i quickly assigned 25 players to each expansion team from the reserve rosters of the existing teams.
then i sat back and watched the AI do the rest. it started by signing personnel over the next few weeks. as spring training approached and started, the expansion teams began signing free agents to fill out the roster. by opening day, the teams were fully stocked.
everything else went smoothly, no unusual errors. the teams, predictably, were horrible, both easily hitting the 100+ loss mark. fairly on the mark
aside from having to come up with some sort of system to simulate the actual draft, i'd like to see the ability to change league structure after the seasons ends, not just when pre-season starts. this way, i can give the expansion teams a bit of a head start in signing free agents and personnel.