My 2c.. I love my drz for exactly the description you gave.. It's my day to day bike, with super moto setup it's probably faster corner speed on tight roads than my fireblade, due to my own fear of the blades power and weight, I can feel like I can dominate the super moto more.. I have both wheel sets so have off rd or Laos rd capability but it stays in sm trim for local hooning as for trails locally it's heavy and I prefer multiple cheaper bikes than one ktm style big ticket one size fits all..
For little money you can add long range tanks, 440 kits, hot cams, and lower it's reliability for more pop.. Your still at half the cost of a wr.. With longer service intervals.. Sure it's not a light bike, but it's solid.. Could do the same with an xr, even more bulletproof but harder to find and limited electrics.. Or a well modded klx.. Tho I feel to really sort out a klx you spend more than just buying the drz to start with, but your upside is ongoing cheap parts supply.. Xr650 or klx650 big thumpers are rare as rocking horse shit.. And too heavy for tight technical trail imo.. Would love one if i could find a good one tho.. The drz's are findable, Phil's got a whole shed of them, pikey had a modded up one for sale for ages, mocyc has them come up all the time..
Grey books, if done well, are a non issue IMO.. It's getting them done, and the book in your name, that's the hard bit, once the DMV have put it in your name your pretty clean. Providing its the right type of book, eg right cc, right manufacturer, and right no of cyl.. Running a 4 cyl liter bike on a 125 single cyl sonic isn't fooling anyone.. Hell I just saw insurance pay out on a plateless bike as the car driver was at fault..
There's no right bike, it's all down to what you ride most, how hard you ride it, how fast you need it, how much you will spend.. I am just biased as I enjoy my dizzy for all round use a whole bunch.. I