Why do you need this, [... rest removed....]
My vision: Install the stable versions in a standard location; for the other versions, ask (and suggest) where the user would like the s/w installed.
The installer already asks where you want to install it, but the problem is that it has a single configuration file for all installed versions, something which was done to follow MS guidelines. I
seriously, people who wants different version can still install lazarus inc:\laz0924bc:\laz0928b
Yes you can install Multiple Lazarus but is hell with config files, and compiled packages, because all this stuff is saved in the User Directory.
What is all that discussion about? a great installer for each of you?
seriously, people who wants different version can still install lazarus inc:\laz0924bc:\laz0928binstead of the default c:\lazarus