Not really. I have suggested this many times in the past.
You can see an entire discussion about this on the following thread, which started on a port25 challenge: Http challange on port 25? - #13 by orangepizza
There are few other threads this has come up on, but that thread covers almost every concept.
I am 100% behind the idea of an RFC defining a dedicated port for an "acme-challenge", as that would handle the problems you suggested. This would require the port to be reserved/privileged, so only server administrators could obtain the certificate.
The big issue is that the "well-known" reserved/privileged ports are not consistent across operating systems and operating system versions. There are a handful of random operating system versions where ports <1024 do not require admin privileges for binding. There are very few ports under 1024 which are commonly privileged across most systems.
@_az has been working on a great idea introduced in this post - Using nfqueue on Linux as a novel, webserver-agnostic HTTP authenticator - which uses nfqueue to bypass port80 traffic to get around the issue of port80 being already used.