I found a way to let MediaPortal pick up remote commands and forward them to the Opera Mobile window.
The best solution will be deduce all Opera Mobile action from standard Media Portal "Action". See configuration for keyboard or remote. This solution will be totally universal and free of any control method.
Dragy, pleas continue, you are at the right way
BTW: Currently I'm using Browse The Web plugin and this one uses described method (though not always
JiRo.