I may sound repetetive but this is an awesome idea... for the house rules section.
Here we discussed the offcial rules as they are and not as they should have been.
The rulebook clearly states...
There are many ways to run a league, with one presented here being just one example. It is up to the Commissioner to decide how to run their league, and they are free to change or modify any of the Blood Bowl rules as they see fit.
Essentially we are discussing official rules...
The official example league are of course to be taken as a good recommendation for a balanced league, I presume the rules were written with the length of leagues as stated by the example they use in the book.
So, a division will contain about 4-7 teams, although up to 8 is possible. That means 10-18(20) games per season and any friendly games in addition to that.
As far as I know these rules are balanced to get teams that eventually will stay around 1500-2000TV from season to season.