I'd like to point out why the mixing of cogs can become more of an issue. Since the advent of shift-while-standing setups, there was an immediate need to reduce the slippage during gear changes. This is because an un-seated rider needs continuous drive force on the pedals or there will be an unnerving swerving when a shift is done "under power".
The slippage I mentioned is hugely magnified whenever an HG-type cogset's staging is interrupted by well-intentioned reorganizing of the cogs, thus I can't recommend it.
For touring and commuting, where aggressive attacks on rolling hills (or sprinting) are de-emphasized, a re-staged sprocket stack works well enough, though will still be more sensitive to cable contamination and/or misadjustment. I'm quite sure this kind of riding is what the late Sheldon Brown had in mind.
I have tinkered a bit with cassettes, one of my 12-25t cassettes gets a 28t added on for hilly centuries. I lose the 13t rather than the 12t though, and don't make the 12-14 shift under standing efforts anyway, so there's a net advantage on those grueling rides. That, plus I just happen to have a titanium 28t cog laying around.