Well, I conducted the higher hydration experiment with the Bosch Universal Plus mixer today.
The hydration I used was 80%, since it was mentioned here in this thread a couple of times. The flour used was a high-gluten flour. ADY, sea salt and a tiny bit of sugar rounded the dough out.
I took three vids...excuse the quality, to show the first mixing stage followed by a 20 minute rest, then mixed for another 5 minutes until the salt was completely incorporated then followed by a 10 minute mix to complete the dough.
The impression I got was that it does handle a wetter dough very well. My KA returned a soupy kind of dough most of the time, so this was a nice improvement, imo. Was it perfect? No, but which household mixer delivers a perfectly mixed high-hydration dough? Some mixers are better than other and the Bosch is clearly on the better side of things.
Like with most wet doughs, it still needed some amount of bench flour to get it shaped but the amount itself wasn't excessive. I shaped the dough into a round, covered it and let it rest for 30 mins on the bench where it almost doubled. The feel of the dough was strong, yet soft and very silky. I degassed it, shaped it again and placed it into a bowl for an overnight ferment.
Overall, I was very happy with the outcome although I had to reach into the bowl to scrape the sides once and it was a bit tedious to get it out of the bowl after mixing due to the bowl's design. But those are two things I can live with.
So, to answer the question here...is the mixer capable of handling a higher hydration formula? Yes. Does it return a decent to good and properly mixed dough? Absolutely. However, I'm also a believer of mixing by hand when it comes to dough with a 75% or higher water content since you'll get your hand wet and dirty anyway.
Another thing is that I believe a mixer cannot be judged by its performance, in regards to wetter doughs, alone. The ingredients play a huge role, mostly the flour's absorption rate, protein content, salt content, etc. With that said, results may vary for others with this mixer just as they would with any other brand mixers.
The Bosch Uni Plus is a superior mixer, imo. And I'm sure it will get even better once I have it figured out and learn about its intricacies. It took me awhile with my KA as well.
I hope this little test answered some questions...