Scale of development reduced: chances for exception?

In my circle of friends, a property is struggling with the following problem:

The building measures were significantly reduced by amending a development plan (and also reallocation to another subarea within it), namely from
II full floors / floor area ratio 0.4 / total floor area ratio 0.8 to
I full floor / floor area ratio 0.4 / total floor area ratio 0.5 -
in addition, on the opposite side of the street, building can be carried out continuously according to §34, as there is no development plan there at all.

On the mountain side, two full floors and a recessed floor project above the street-level "underground" garage,
and on the valley side, only a bungalow is now supposed to be built.

How do you see the chances for an exception here
a) back to the old status valid until three years ago
b) exclusion from the scope of the plan for the purpose of applying §34 as on the opposite side?

It would be interesting to know why the [BePlan] was changed. Maybe the municipality wants to curb the somewhat too tall city villas/2-story buildings a bit? One exception leads to a second exception... what should the argument for the exception be? How many square meters of land are we talking about?

I am currently researching the history. There is a dilapidated shack on the property that is older than the first development plan from 1968, and whose eaves height is at street level. The replacement for this building would preferably be brought up to the street with a parking length distance – like the neighboring houses. According to the old plan (II full floors) one could have at least raised the roof by one floor and had the upper floor at street level, albeit set back about two-thirds of the house depth behind the neighbors.

There is no plague of city villas there.

We are talking about 532 sqm = 212 sqm floor area ratio before / after and 424 sqm / 266 sqm plot ratio before / after; but more importantly, previously "ground floor possible at street level" and afterwards "ground floor at street level would have to be on stilts, because the basement alone would be a full floor due to its protrusion."

How do you see the chances of an exception here

The owners should have been more involved in the public participation. Once the amendment is legally binding, the obsolete provisions no longer matter, unless legal action is pursued. But you yourself always write this in other threads:

Post the plot and the development plan excerpt, then you can see more precisely.

Just post the development plan, and preferably also a Google Earth image

Then post two things here, namely a development plan excerpt with the plot

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