Increasing floor area of different masses

We have a masterplan which is composed of different masses which are divided in families with different shapes (as you can see in the attached picture). These are parametric masses in which we can change some parameters like depth, height etc.

We want to increase the floor area of each mass of 10% but we don’t want it to increase in every direction, in fact we want to move only the RED surfaces and to keep fixed the blue ones.

Clearly the offset tool is not suitable cause it moves all surfaces and of a unknown (we don’t know how to calculate it!) value.

Ps. There are too many masses to do it manually, we want an automatic method for all them.

Thanks! Elena