@ 40 for reliever fatigue -- Here's how it works out :
pitches/ fatigue %
15 / 65
20 / 53
25 / 41
30 / 30
What this does is not allow a reliever to work three consecutive days; One scenario : 25 pitches day 1, at day 2 fatig % will be 78% ---- if pitching 20 pitches on day 2 then day 3 fatigue % would be 64% ; Obviously this would not allow you to use a reliever three days in a row.
BTW starters at 40 fatigue (while simming) still recover to 100% after 2 days rest.
The only way that you I can see making fatigue work correctly in a season is to adjust it manually during a game: put it at 12 for starters and long relief (you may have to make pitch control easier during the starter's pitching O/w you will not make it to 100 pitches); 25 for middle relief; and then 45 for setup and closers