I do want to emphasize the tongue in cheek nature of my diatribe as indicated by the line at the end. When it comes to 40k fluff, my take is always filtered through my 'Black Legion Apostle / Abaddon Fanboy' filter. While I disagree with the less warp-influenced, more traditional 'traitor' rather than 'chaos' marine take on the faction, and I feel trying to cater to that concept in the 40k CSM line would be a mistake, I am glad that the 30k game and especially model line exists to provide toys for those players of the opposite opinion, and I'm glad that the new multipart CSM stuff has supposedly been designed with an attempt to maintain at least some compatibility with those models for players who want to split the difference.
Your long post above is great and I respect where you are coming from. A counter-point (in a friendly way, I honestly don't care too much either way) could be that having a Chaos faction or two in 40k that bucks the "warpy" tend and comes off more "normal" can be a nice aesthetic balance...similar to how Space Wolves can be conceived as a "wild" aesthetic balance to the traditionally more "controlled" Space Marine factions.