I am leaning towards the 12 team league. Expansion later to 16 teams is a difficult process, but we'll definitely want to do that as soon as there are sufficient IP's.
Yes, with only 12 teams there will be no need for 1900's pitchers as the 20,128 IP's spread over 12 teams is 1,677 per team (for 16 teams it was only 1,258 per team).