If you need two dishwashers, then have two installed. I would loudly ignore the opinion of others. However, I would think very carefully beforehand whether the second dishwasher is really necessary – also for space reasons. This sounds horribly pedantic, but it worked for me too: just try to get into the habit of emptying the dishwasher immediately when it’s finished for a week. At the beginning, when I had my first own dishwasher, I also kept putting it off until there was so much "new" dirty dishes on the counter that it became too much for me. I even timed how long it usually takes to empty the thing: I was done in under two minutes (a good, sensible arrangement of the dish cabinets helps here too). Nowadays I use the short program during the day; the machine is done in an hour. On my Siemens, the running time and the end of the program are projected onto the floor.
I would really fear that on the one hand people become too lazy and hardly ever empty a dishwasher anymore and in the end both dishwashers have finished running, both are only half full of dishes, and new dirty items come in that want to be loaded. That results in even more chaos than before – don’t let it get to the point where you stack clean dishes from dishwasher 1 into the clean, half-full dishwasher 2 to be able to reload.
If I think it through like this, two dishwashers that are in everyday use ultimately require more discipline than just one. For parties, etc., however, a second dishwasher is undoubtedly a good thing.