This ignores the fact that pretty much all players use .5 as a transition to becoming a full TH whatever level. Our .5s face full Ths of their level as often as they see THs a level below. I wouldn't think much of a clan that builds a bunch of .5s that stay that way indefinitely, but it's just not that big of an advantage.
The extreme lopsided bases can be a much, much bigger advantage. They do require some thought about how to prioritize certain troops, as well as how to integrate them into the lineup to ensure war MM brings favorable matches. But, it's not rocket science. And, I don't see many lopsided th11s that haven't been heavily gemmed. Based on some comments & the general attitude of folks defending extreme lopsided bases, I suspect many of the non-gemmed ones were farmed with bots, not human effort. You're speeding faster because you've bought a Formula One car & challenged guys who tinker in the garage to a race.
.5s might see a slight drop in their advantage, but it's already a pretty small one in most cases. Extreme lopsided accounts will be hit harder. I suspect there will always be an advantage to having troops ahead of your defense, but you guys won't be able to buy your way to ridiculous win streaks.

