A workaround suggested to me by @Adam was if you skip the homedir but then add the mail directory, you should be able to import the cPanel account and then rsync the files from /home/[user] (cPanel server) to /var/www/[container] (Enhance server):
/scripts/pkgacct --skiphomedir [user]
tar -rvf cpmove-[user].tar /home/[user]/mail
Replace [user] with the cPanel username of the account. This should result in an importable backup, and if that's under 10GB size it should be fine after you rsync the files and set the proper ownership and permissions.
Since the email would presumably end up in another container, even a different server, you might need to skip the mail directory in the rsync to save that extra storage or remove it after import.
I have yet to try this, but I'm supposing it should work. If I try it (not sure when) I can confirm.