bootAble is a fine product, and I really thank the authors for a job well done.
The job is not "done". BootAble is a work in progress. Unfortunately, Hayo Baan (the original author, and main programmer) no longer actually uses eCS, so he only does work "on request", using eCS in a virtual machine. He seems to be quite happy to help, but he cannot actually do most of the heavy digging to determine what is needed to make something work. He has, of course, donated his work, because the "source" is in the distribution, but he enjoys the opportunity to "clean up" donated work.
To make some more universal boot, there would need to be some kind of preboot work
True, if bootAble was designed to be more "universal". It is designed to be specific to an individual machine. The eCS boot CD is almost the same idea, but it is designed to be "universal". Unfortunately, "universal" keeps changing, so they do have problems keeping up.
With a bit of work, you could copy the eCS boot CD to a folder, remove the eCS install stuff, and add your own. A change to the STARTUP.CMD should be sufficient to change the operation, after it gets booted to eCS. Then burn the new setup to a CD. I haven't done a lot of research about that, but it should be relatively simple. You could also leave the eCS installer stuff, and add your own software, then burn it to a DVD (so there would be room). Some sort of selection in STARTUP.CMD would be able to switch to any package that you have installed to the DVD. It could be an interesting project.
The eCS installer approach basically runs a simple program to detect what devices to select, then gives the user the opportunity to change some of the selections. That ends up changing the CONFIG.SYS (and probably the INI files) to build the desired system. BootAble selects the CONFIG.SYS entries, and INI entries, that already exist, and builds a system to match. The two approaches are very similar, but not compatible. However, bootAble can be manually defined, and with some careful selections, it can be made pretty generic, and it will run on a lot of machines (possibly with a couple of boot errors, which can normally be bypassed). Just make your selections as generic as possible, and you should be able to make it work.