I realize that in the past, people were able to dual-boot their Android 2.2 (froyo) Phones with Windows Mobile 6. But now I don't find any threads or helper documents out on the web with people doing that. It could be just lack of interest. Is it still possible to have a nice Android 4.0+ phone, but with the ability to boot into Windows Mobile 6.5 or earlier generation? Even Win Mobile 5.0 would work (possibly an even earlier generation of Windows CE would work). I have an app that only runs on that environment.
On another forum, I've found that the phone to get is the HTC HD2 for dual-booting Windows Mobile 6. Because it is the one of the last phones that came pre-loaded with that OS. Then you can boot from the SD-card into Android. However, to get (t9193) one that works with the at&t network is extremely expensive... people realize how rare these phones are, and that they are only from Austrailia, and for uber geeks, that they mark up the price to 600+ American dollars for a used one. The cheaper t8185 will not work in the US on the 3G networks. There are some rare tmobile versions, but they will not work for me. It is all to do with the 3G band (hardware locked on the logic board).
Also I don't think anyone has figured out how to boot Win-mobile 6 from their Sdcard, meaning dual-booting the other way around.