We have reviewed this internally and unfortunately, will not be able to go ahead with it due to the reasons listed below;
It seems hard to use ssl from letsencrypt has no tab in ISPconfig , it needs to be done manually for each website.
DNS records should be added manually for each site
Roundcube has issues and it needs to fixed individually on every installation
There is an alternative you can try out, VestaCP and we are also working on rolling out FastPanel soon