Sure, I automated it for a slightly different setup: I have two web servers, both being able to host my sites, but at any one time only one of them has DNS pointed to it, the other being hot standby. In order for letsencrypt to work also for the the standby host, I’m using apache’s rewriterule with [P] proxy mode to let the ‘real’ site serve the challenge, if it does not have it locally, serve the challenge anyway proxied from the hot standby (where apparently letsencrypt is currently running).
Specifically, I have on the webservers, in the virtualhosts on server A:
RewriteEngine on
RewriteCond /srv/acme/challenge/$1 -f
RewriteRule /.well-known/acme-challenge/(.) /srv/acme/challenge/$1 [L]
RewriteRule /.well-known/acme-challenge/(.) http://acme-B.example.com/$1 [P]
And on host B I point to acme-A.
acme-A and acme-B are both working http sites at respectively host A and B serving only the local challenges of A and B without any redirect logic.
If you have more than one, you could at considerable reliability and performance costs daisy-chain everything together, or creating something more fancy (such as uploading the challenge to a central location and each site serving challenges from that).
(note: I’m using acme_tiny.py, because it does precisely what I want and is IMHO quite a bit easier to install and use).