Now, syslinux 3.51 is out, and it supports two new directives, one is to include another config file in syslinux.cfg (MENU INCLUDE), the other is to start the menu from scratch with another config file (CONFIG).

So what I suggest is to put the slax kernel and initrd image and it's syslinux config file in the /slax/ directory, so that /boot only contains syslinux files. And by default /boot/syslinux/syslinux.cfg will only contain a MENU INCLUDE /slax/syslinux.cfg .. but people could more easily customize this.