>> implementing ActiveSync wouldn't be that difficult to achieve
The issue, as I already explained numerous times, is having to get a license to use ActiveSync from MS:
1 - the complicated logistics
2 - costs
Look at Boxer. Got a great start, marketing, promotion, and now seems to be going nowhere. Lots of complaints in Google Play about its price -- and a then separate purchase to use Exchange.
They went with ActiveSync, and have to cover their licensing costs. But it does't do anything to change how users see it ("I have to pay *twice*?").
>> doesn't support Active Sync
ActiveSync is just a network protocol.
Can you explain why the network protocol is so important to you?
Maybe rather than a network protocol, you have specific Exchange oriented features in mind?