Unlikely that it would be, as ACME v2 is very new (and I don't believe it's yet supported by the production server)
It's really a pretty rare case where a wildcard cert would be needed. In most cases, you know what hostnames you're going to use, and they don't change. In those cases, no, there's no reason to bother with a wildcard cert--just issue a cert that covers all the hostnames you want. This has been possible since the system went live two years ago, and covers the large majority of the cases for which people think they need a wildcard cert.
If your host now supports Let's Encrypt, what I'd advise would be to request a single cert with all your hostnames on it. Presumably your host's support includes automatic renewal, so once you've done that, you're set.
Without knowing what "manual method" you've been using, I can't say for sure, but most methods I know of do allow this.
I am also waiting for the wildcard certificates to be available.
I would like to ask you about this:
Would this work if I do not have access to those subdomains from the machine where the certificate is issued? A simple scenario for this would be requesting the certificate from an EC2 instance that resolved from www.mydomain.com and I also have a CloudFront distribution at static.mydomain.com and an ELB at lb.mydomain.com.
Would it work if I am asking the certificate from that instance for all these subdomains?
You’ll need to use the DNS challenge to get a wildcard certificate anyway, and if you have that ability, you can use it now to validate each individual subdomain. The DNS challenge can be completed from any machine that has access to your DNS API credentials.