But unfortunately, the development plan and also the budget do not allow more than 109 sqm of floor area or 155 sqm of living space. [...] The question is whether the architect can really conjure up anything better here considering the framework conditions (see above). The general contractors don’t have their "standard floor plans" for nothing, and I am somewhat concerned about investing a lot of money in an architect and ending up with a similar floor plan in the end.
The attitude that an architect is only worth his fee to the extent that his floor plan is more original/smart than what one could achieve without him is as misguided as it is widespread. It is based on the misinterpretation of the architect as (at least essentially) a floor plan designer. In reality, he "earns" his money (through sweat) mainly in the second half (service phases 5 to 8). The floor plan accounts for only about one fourteenth of his fee.
The "standard floor plan" of the 610 already has 112 sqm without the "bay window" and is designed for a "normal family" with two children. Here you have apparently already tailored it a bit more narrowly in order to still meet the 109 sqm limit with the "bay window," and then also added another room. I am somewhat amazed that this still works relatively unscathed. Nevertheless, it is only an impressively realistic imitation of the actual standard floor plan, because they have only proven themselves under the condition of maintaining the standard dimensions (and without complicating the layout). In addition, a standard design loses a significant part of its advantages if it is copied by another contractor. From this perspective, I am even more surprised at how little worse variation 3/R turned out compared to template 1/L – apart from the less favorable bathroom location. And design 2/M also deserves recognition from this point of view, since it only disappoints on the ground floor. However, on a back courtyard building plot, a planner quickly reaches his limits in what can be achieved by mere Rubik’s Cube turning. Here the structured approach of an architect has a higher chance of success.
If you want to build on a catalog design, the strategy of cutting and narrowing an approximately suitable starting model is not the best, and here it has still turned out surprisingly well. The more favorable strategy aiming at a 109/155 sqm house for a family with three children would be to select a basic design (since all of them are designed for two-child families) with about 90 to 95 sqm of floor area and extend it along the ridge axis by the third child’s room (see the section "Additional space by enlarging the floor area" in my blog post "Changing the size of a floor plan").