@Lemieuxfan I have ridden several long days, (my uncle lives in Maury County TN which is just under 700 miles from my place in VA), I do that ride right at 10 hours in the full heat of summer with no worries on my 2014 R3T.
@Joesmoe mentioned me above and I now have 54K miles on the bike. The touring seat is different than yours, but as mentioned, I love the BeadRider in the hot months. I rode to Sterns, KY for RAA East 2018 a few months ago at 530 miles from the house, again, no worries for the long distance one day ride. My longest ride was from here to Denver in 33 hours 1700 miles, but I did take an 8 hour break over night.
I too would like a sixth gear as I usually ride around 80-85 mph, the bike just feels good at the speed.
For ergonomics, my opinion is the stock bike fits me well. I am 5' 9" and weight between 210 and 245 (seasonal changes you know), the stock windscreen fits my noggin height quite well.
I did not want a luxury bike when I bought this one new. I wanted a bike that would be my daily ride, my two-up weekend getaway and if I got a wild hair and wanted to go coast to coast, it would do the job. The R3T fit the bill well. When I look at the fancier bikes, I see them as just having more problems to fix down the road with all their artsy-fartsy gadgetry.
Back in 2015 I think, I spent a full day on a 2007 Classic Tourer down in Arizona, I seemed to like it quite a bit as well. It had a layer of wool on the seat which made all the difference in the world for that hot environment. (Thanks again
@TURBO200R4 for allowing me that break from my work then).
We are two different people of course with different views on what is best for each of us, I hope my experience is of value to you.