Yeah I proposed a similar thing earlier on I think (not sure if I actually posted it here - was before I was even running for GPC)
Downsides are when you get bigger
I recently participated in an OP on Helio, I had 30 full nukes landing before the CS. This would give me -30 near the last attack, which would be the one that potentially catches the snipe. Combine that with -30 luck, defense buffs and desire and you haven't got much of an attack left
The only way to then avoid that would be to send less attacks, maybe only keep the ones within 3 seconds which still usually leaves about 10 attacks
The problem there is that stacking before the CS gets way more effective, as we now have less clearing on top of the reduced strength
Another thing would be siege breaks
Say I have 100 odd ls cities as the alliance LS builder, does that mean that near the last attack I wouldn't do any damage anymore? My team counts on over 30k ls but my effective count would be just above 15k
A possible solution is to only implement it on attacks with less than a certain % of the available troops, but then people will just spam with that % + 1 unit
I like the idea but it definitely needs some work