Possible partial workround for you to try:
Is there another command (aside from "Power") that inititates a function - like, say, a channel number (or other) - BOTH if the unit is off and if it is already on?
If channels work like this, so that pressing 1 (for example) from off will turn it on and tune channel 1 then you could use that in your sequence for the initial power on; it would be ignored if its already on and on Channel 1 else it would simply change channels - i.e. wouldn't affect the power state if it's on already. And then send the rest of the commands.
You'd only use the Power command for "off". If you write a sequence that precedes that with "1" again, followed by a pause to give it time to boot then that would similarly ensure it was ON before the power command is attempted to turn it off and similarly would be irrelevant if it were already on.