Lowering it much castrates it depending on your riding style. I like it a bit sporty in the twisties. Lowering would really suck for my riding.
Lowering an inch seems to be the most that is "safe" and "reasonable" and doesn't appear to pose any danger or reduce cornering much; at least on a gen2 with a non-heavy rider. But I absolutely think lowering more than that is not just going to ruin twisties, but pose serious danger from bottoming out, pan scraping, front fender hitting.... stuff like that.
Why buy it to ride straights all the time? You would be wasting your money.
Not necessarily. There are LOTS of loud, low-performance, low-tech, annoying, vibrationy, Harley-type bikes out there on the road... many of which would be completely inappropriate for "twisties", yet quite friendly for shorter legged people. However, one might want a Concours for all the other things in which it is
so much better than "cruisers"- smoothness, power, quietness, technology, reliability, style, weather protection. Even if it means losing some cornering due to lowering.
Not everyone has the same riding goals. I know you know that, I am not picking on your post. I am just clarifying for those people who love to yell out "maybe this bike is not for you", wrongly thinking there are lower-height alternatives out there that retain all the things that a sport-touring bike can offer. Personally, I would rather have no bike at all than some V-Twin thing.