No, I understood perfectly what you
want to do. You can't do that, obviously.
What I was suggesting was a way to do the same thing, or very close to the same thing anyway, with the current system.
He wouldn't need to know what was on your planets, if you didn't have any planets.
SO you give him all your planets. You keep the ships, and do all the grand admiral poobah stuff like fight the wars, and political communications with the enemy. He has all the planets under his control, so he takes care of moving poulation around to maximize resource production and construction, research, all that boring stuff.
He doesn't have to worry about protecting his planets, cause you are doing that with the war ships under your control. You don't have to worry about keeping up the resources, cause he is gifting you all his excess every turn, and building warships and gifting them to you every turn.
You would only need a few planets, mainly for resources storage, not production, and you would need at least one of course so you could remain in contact with the other races.
It wouldn't be one empire like you wanted, but it would be two interdependant empires in a symbiotic relationship with each other.
Not sure if anyone has tried it on that level before, but it would be fascinating to see if it could be done. I mean I know technically it could be done, but it would take a lot of coordination.
Geoschmo