2) Given the existence of dx, why go to the lengths of creating your own Java/Dalvik language compiler - just use an existing Java language compiler and bolt the dx tool on at the end to convert the newly generated Java bytecode into Dalvik bytecode. No need to reinvent the wheel.
Unless anyone can state categorically that Google have their own clean-room Java language compiler which spits out Dalvik bytecode without generating intermediary Java bytecode I think Google may be on a slightly sticky wicket.