So in fact the principal reason for using gksu is for backward compatibility - your script will work on some old system that has 'gksu-legacy', and on the other hand some old script written last century when gksu was all there was will still work.
However, this gap in ktsuss's functionality seems like a pretty big one, especially if it can be fixed by a little wrapper script. I just had a look and the meat of it is only about 15 lines long. So I'm guessing it's intentional to separate out the graphical su capability from root environment inheritance - simplicity as in "stupid!"
The developer of ktsuss, nomius, also appears to be behind kwort, a Slackware derivative (via Crux) with no drivers or firmware. If Salix is "Slackware for lazy slackers", Kwort must be "Slackware for masochists". Even by copying the drivers and firmware from the Salix partition, which is surely cheating, I couldn't get it to work. Yet I dimly sense that there's something pretty cool about it ...
I got that wrong - it used to be Slackware-based then changed to Crux, which I don't think has a Slackware origin. That was when the drivers and so on were ditched in the name of simplicity.