Effort is beyond abilities of average ISV

Again, we have those in Linux (e.g: klik). And they are not popular, for a good reason.

next->next->next does not include the time it takes to:
* Locate the software
* Verify that it is not a trojan

The mere fact that you have to ask the user questions is a usability bug. In Debian it was
fixed long ago with debconf: a standard way to ask questions. With priority (so you can tell
the installed package to only ask important questions, or ask all questions) and you can
provide answers in advance.