Case solved!!! What initially seemed impossible to us, namely eliminating 3/4 of all mentioned criticism points (those that convinced us) without a complete redesign, has actually succeeded! Thanks again at this point for your opinions, considerations, and efforts that you put into finding solutions (some of you managed to inspire us with new ideas or to further develop solution approaches). Even though it was really tough at the beginning and brought us down a lot, the honest opinions (well, some could have phrased it a bit less harshly, the tone was sometimes quite borderline! ... Maybe as a suggestion for future help-seekers ;)) were incredibly valuable and ultimately led to us now having a really good feeling about putting our current plan into action! :)