Sorry, all wrong
The favorite quote of "my" regional managing director is: "if you want to build a ship, don’t give your men a blueprint, but teach them the longing for the great, wide sea."
In this sense, you first have to instill two feelings in your row neighbors, namely "Goalkeepers are nice" and "Goalkeepers already know more about the topic."
You must not start with the roof shape as a technical parameter: with "gable roof or flat roof with attic" you misdirect the conversation onto the factual track. You can only inspire your row neighbors on the emotional level with empathy to wish your row a shared roof.
Fire compartments are of course necessary, but a common carpenter and a common roofer are already a favorable situation (for this seamless goal).
Ideally, there are four parameters consistent throughout the entire row: 1. equal zero height of finished floor edge, 2. equal story height, 2a. equal height of the wall plate (knee wall height), 3. equal building depth, 4. equal roof pitch.
"1." recommends a common foundation and, if necessary, basement builder (you can be a mixed group with and without basements, that is not hindered by this). Without "2.", "2a." and "3." "4." is not completely useless, but already significantly less beneficial.
Within this framework profile there is still plenty of freedom—theoretically even enough so that everyone could build exactly what the other would find the ugliest. So at this point the most important message is: consideration for the other row neighbors does not restrict anyone, so it does not endanger anyone’s house dream in terms of taste.
The goal of the first meeting should therefore be the group feeling, so that no one feels the need to act like a stubborn individualist.
At further meetings, it will be helpful to let others take part in the fact that compromises must also be made with you, and for example the corner whirlpool is left out. This reconciles the neighbors with their compromises and prevents these from being felt as charged to the “harmony with Goalkeepers” cost center.
Ideally, the feeling will develop among the row neighbors that it is actually really a shame to "have to" choose the builder oneself and that it’s best to take the one from Goalkeepers (although each individual trade can be taken out and awarded differently or done by oneself!).
At a following meeting you can present a visualization of how visually different the individual houses in a row with such a common profile could be designed. What is unproblematic, for example, is mixing monolithic houses with ETICS houses or different preferences for bricks.
If there are no idiots involved, I don’t expect any trouble at first.
What you do have to "expect" though (you said the neighbors are still newbies in building matters) are classics of false assumptions like "prefab houses go faster."