Your alternative is an interesting take. I agree it's not a major priority, but there has been a lot of talk on SN lately about expansion and improvements. The devs are good; I'm not worried about it being a struggle for them to implement.

As to the questions, I think if you merge fast enough, then there aren't any comments to worry about. Also, this typically happens with external content links that don't get a lot of reaction here anyway. I wouldn't worry that dozens of posts would merge and be incoherent. The merged posts could be tagged [MERGED] anyway.

Zaps allocation is up for debate, but I think the first to post wins the pot. People reposting shouldn't be rewarded; they should be penalized.