The current rule is not far from what you describe. I'm not a fan of restricting when and where you can play guys. Apply penalties, if need be, but leave the decisions to the manager. I'm not sure if you know it but here is the current rule from the manual on platoon players.

Platoon Factor: Players (batters) who are rated Platoon L (Stats/Rosters-ratings page) are limited to their actual plate appearances versus LHP. After those actual plate appearances, they will become very poor hitters versus LHP. This is to avoid the phenomenon of a left-handed batter who batted over 300 times versus RHP and only 10-15 versus LHP and got lucky for that very small sample of plate appearances.
The same thing applies to Platoon R for their plate appearances versus RHP.