Removing second attacks in Clan Wars
My suggestion is to remove the second attacks in clan wars. This would have the following benefits:
Making 3* meaningful at th8/9 again
The present system is weighted towards offence which has led to wars getting stale at th8 and th9 where most/all bases end up 3*d on second attacks. Removing second attacks would remove the mop-up attacks, making 3* attacks at TH8/9 meaningful again. And making them *huge* at th10/11.
Make base design worthwhile
Removing second attacks would restore the balance between base design and offence. Careful placement of traps, teslas, and cc troops choice may trip up an opponent once, but really what's the point in investing time in base design if there's a second attacker who now knows all this and plans accordingly?
Eliminate scout attacks
'Scout' attacks are where a clan includes a low th account (eg th6/7) that is used solely to scout for cc troops/traps on an opponent th10/11 base. This is viable because another player can use their second attack to hit the base the low th account did not attack. Removing second attacks creates an opportunity cost for scouting, because to do so means not attacking another base.
Reducing incentives for 'engineered' bases
'Engineered' bases are where players keep defences low and max out troop levels. This is beneficial in the current format because a player can attack twice but their base can only be 3*d once. Without a second attack, things are more even - the engineered base has one strong attack, balanced by a weak base that's easy to 3*.
More exciting wars
Every attack would count, every one. You know that feeling in war when you're the last player to attack in your clan at the end of a war, and the clan needs another star to win? That's what every attack would feel like.
Shorter war formats
Wars could also be shorter. Reduced cook times for troops and spells, combined with a single attack for each player, means wars could be concluded in 2-3 intense, exciting hours. Great for content streamers, too!
More frequent wars
Prep day could also be shortened, allowing for more frequent wars.
This should appeal to the 'elite' war community, as it would be a truer reflection of player skill. Plus, elite sports in general don't allow a 'second go' - you're either the best on the day, or you're not.