Hmm, rewriting the fluff to justify uniform knights does seem a bit lame. If a player wanted humans in uniforms they could already build an Empire force. From my perspective, one of the fun things about the Bretonnians is the individuality of the knights, contrasted with the abject poverty of the rabble. (Honestly, it has been a while since I paid much attention to GW’s lore for the setting- they kind of lost me when the Old World got wiped out and replaced with planes, or dimensions, or whatever.) You’re definitely right about uniformed knights, like crusading orders, having intimidation value. Adding a couple knightly orders to the new Bretonnians could be cool (or adding uniforms to the fluff of the existing orders).
Time will tell whether the changes resonate with the buying public. Personally, I’m still working on my late ‘90’s-early 2000s backlog and those knights will be getting individual heraldry!