No, you can't change it for AOW. The CMAS 1* cert, as I know it, is virtually identical to the PADI OW cert. You should, however, be allowed to enroll a PADI AOW class if you have a CMAS 1* cert.
What I find interesting with the agreement is that in reality there are lower demands on crossing over from PADI to CMAS than climbing the CMAS ladder. A PADI AOW is below a CMAS 2*, as the 2* syllabus - again as I know it, there are national differences between CMAS certs - includes a bit of the PADI Rescue syllabus. Even though I have PADI certs, I'm quite convinced that the CMAS syllabus and, more importantly, the amount of hours spent in a CMAS class, generally is better and more extensive than PADI's syllabus. Also, the number of logged dives required for a CMAS diver to enroll a higher level class is larger than the number of dives required for a PADI diver.
Since my first cert was PADI OW, I'm currently climbing the PADI ladder. However, I see no reason at all to continue in the PADI system after Rescue. The PADI Rescue syllabus seems to be more extensive than the CMAS 2*, so that's a good thing. OTOH, I have absolutely no intention of "going pro", so the DM course doesn't fit me. CMAS 3* is a certification very similar to PADI DM, but it's geared towards non-profit club diving. I see a lot of value for the recreational (i.e. not-for-profit) diver in learning how to be a competent divemaster/dive leader, so the CMAS 3* class would fit me a lot better. If I ever take another class after Rescue, I don't believe it'll be given by PADI. I would, however, seriously consider CMAS 3*.