actually looking at the formula as long as two or more servants are always working on a room you can be super efficient and work ahead of the curve. Think of the percentage as how efficiently you'd be working as one person.
One small issue, the character switch is in a cycle. If the next in the cycle is in a room you can't switch characters which is a pain if the only other squares are the kind which the current character is weak against
Ok, even taking into account that this is aimed at kids there are hundreds of these kinds of games they're basically the same game with different pieces to decorate with
Uh lee, whenever someone makes something there is an automatic implied copyright called intellectual property. So unless the person who made it died 50 years ago it is copyrighted