it will be very usefull to port it to Lazarus
Im just taking a look at the source of InnoSetup...
And the conversion from Delphi to Lazarus do not create a miracle

Lot of work to only convert it...
Maybe the fastest way will be to recreate from nihil a LazInstaller.
-1 choose a look-concept.
-2 define ability to create Windows, RPM, DEB, Mac and custom packages.
-3 define the file-adder.
-4 define the compressors.
-5 define the tasks the installer must do.
-6 define icons and short-cuts to add (depending of os)
-7 define the uninstaller
-8 ...
Lazarus setup is created with Inno Setup,
Do you know what created Lazarus setup for Linux ?