Being able to modify city building's passenger and mail level
would open new game behavior possibilities.
Currently, commercial tagged one get X2 for mail level, industry one for half.
Passengers level is same/proportional to base level represented by /1000 of
removal cost. (or something similar to this)
For example, one can apply x5 passenger value of base level for commercial
and 1/2 for residential to make commercial city building much more attractive
compared to others.
This will make more definite passenger flow pattern
if certain city contain more one type among com/res/ind city building with
more same type coagulation inside the city.
Some mixture of these new parameters can create more interesting passenger
/mail flow variation possibilities.
(new parameter like modifiable destination percentage. which we have
50% for city building, 33% for industry building, 17% for tourist attraction)
(another parameter is different city prefer building one type among res/com/ind
than the mixture of all, all the way keeping res/com/ind balance all map wise)