A few answers to questions above.
OMA+SSL
As Rob says above, there should be no problem getting OMA to work with SSL. All devices listed as supported by OMA, have also been tested using SSL again IIS.
OMA vdirs
It is possible to rename or create new vdirs for OMA and EAS just as it is for OWA. It's easiest to do this through ESM. You can also make OMA and EAS use some other vdir than /exchange to access backend data by using the
"HKLMSYSTEMCurrentControlSetServicesMasSyncParameters
ExchangeVDir" registry key on the FE machine. Set it to ‘/mailboxDataAccess’, or whatever the name of the BE vdir that is exposing DAV+OWA is.
Modifying OMA UI
It is true that E2003 OMA UI on PPC/Smartphone isn't as good looking as it could be. OMA was written with the goal of having it work on as many mobile devices as possible, and making it look great on richer devices wasn't a high priority (especially not for PPC/Smartphone, where great Exchange access through Pocket Outlook and EAS is available). Unfortunately there is no good way of modifying the OMA UI.