yes i think there are still chances. you can always try - call
the ARC to find out. you won't be stripped of your rank, although
when you are on course (say, CCC) you won't be exactly wearing
them. and you prob won't go through their BMT again. you will just
go for their conversion course.
but do you know exactly what the commandoes do? and are you sure
that is what is for you? what are the pull factors attracting you
to sign on as a commando?