My comments were in regards to turning an 850 to an 1100. So we were talking about changing out pistons, cylinders and heads, not accessories. But to answer your question, yes, i have done all the things you describe and I see nothing wrong in personalizing a bike or improving it.
Well that was sorta my point. One guy might just add a windshield and be done. Another guy might 'need' more changes to suit him.
And still . the engine mods aren't that extreme ? {IMO} so a person could end up with a lighter weight, low seat height , six speed motorcycle for a lower cost ? Depending on the deal of course & how he goes about it.
Would I ? No , not unless I got a heck'of'a deal on an 850...and wanted something different or thought I needed the 10 extra HP. Not sure about up north ? but down here they are much lower priced than the 1100....and I'm [told] for younger riders a huge insurance break ? Unfortunately that is not a concern of mine as I am....un-younger