An installer basically is not so different in regards what a user
would do autonomously. For the postinst, for sure there are a couple
of things that would be nice to setup in advance, such as the quantity
of memory dedicated to the jvm and the destination of temporary files
(often the default /tmp is not enough for practical uses). AFAIK
that means adding some .vmoptions files under the binary directory
(e.g. /usr/lib/esa-snap/bin) for snap and gpt.
Even, the snap install needs to be run in unattended mode (-q) with
a custom configuration (and one should also manage the irritating confusion
among ESA Snap and the snap tool, so people should live with the renaming
of snap into esa-snap).