In essence, we already do this, but the dropping takes place in the 2nd round. Corbin and I debated this exhaustively a long time ago in one of the previous thread versions.
The problem with first round drops, chiefly, is how much more pressure it puts on the top attacks to go perfectly. If anything go wrong, then you have a dearth of attacks to rectify the star deficit. Also, if anything goes wrong against #1 and #2, you're pretty much screwed there. You get no second looks.
Secondly, you have to look at the parity in our TH9 offenses. Yeah, the higher guys have much stronger heroes, but that doesn't mean even the lower TH9's are gimme wipes if they are well-designed (as we have seen in the past). So dropping doesn't really guarantee wipes-- only, perhaps, a slightly superior wipe ratio. It does guarantee, though, that you hang you bottom attackers however many deep you dropped. Conversely, by attacking straight across, you see where you did the most damage, and then drop with far more precision according to analysis of how the first round went, and what villages attackers below you ultimately left as the weakest subsequent target in the chain.
If I thought 1st-round dropshifting was more effective, I would do it, but Corbin and I debated this in such excruciating detail back in the day that I was able to sound out everything from the ground up and fully form my decision based on the depth of that reasoning.