For the sake of keeping things simple for Football scheduling, I would think that the EIAC would prefer to bring in a even number of teams, in all other sports 9 schools isn't a problem really. A second team to come with Harrison would be tricky.. I honestly think if Taylor (OH) was looking for a home they would be a great option as they fit size wise and geographically, but they have a stable home for the time being. I think the only real option at this time would be adding Madison to the conference as they are independent I believe, but maybe as a football only member due to travel considerations. From there you can split the EIAC into two and have 1 crossover game so every one has 6 league games and 3 non league games (Harrison would have 4 non league games as Ohio is 10 weeks for football, they would have to find a week 10 opponent).
EIAC 1:
East Central
Harrison (OH)
Connersville
Batesville*
Lawrenceburg
EIAC 2:
Greensburg
Rushville
Franklin County*
South Dearborn
Madison (Football only)
I think overall this would work well IF kept to football only. But some schools might have concerns with travel to Madison.. You could swap Franklin County and Batesville to make travel a little bit easier, but I don't know if Franklin County would be thrilled to be in that division.