holly crap, it took 1 minute to boot!
my improved 3.9 ++ setup with the neccesarry boing bags and modules, like those you propose (+powerwindows and so on) has originally booted on my a4000 within a minute or a bit longer. it was booting from ssd and from the csppc tuned up to almost 40mb/s throughput. i have read of many people having similar boot times. dont even ask how long does os4 boots not only on amigas but on dedicated hardware.
now, once i have got deneb and put kickstart and all the modules in its flash, and the machine didnt need to reboot my bootup time went down to something around half a minute. note that i had a bridge on internal ide to prevent boot wait there.
so, it think aros soft booting from an internal ide of an amiga, which is 10-20 times slower than cyberstorm scsi and with a lot of debug output to serial as you see isnt that bad in comparison? no doubt the boot speed as well as overall responsiveness is not good enough, and needs to improve. but this involves work. and i am showing the current state of what im working on.