If they knew they were warp capable why the need for secrecy, why not just ask the Ba'ku to move?
Oh I agree there, except the baku shouldn't have been "asked," they should have been told to get their shit together, because they were
If you want to explain the situation ... fine.
If you want to help them in the move ... fine.
But the Baku needed to leave for their own safety, because the ring were going to be harvested. It's like the people living behind that brand new hydroelectric dam, once the area behind that dam begins to fill with water, for their own safety, those people have to leave. One way or the other.
Normally when the government wants the land you own, they have to compensate you. They don't go around stealing it.
Problem there is of course the Baku did not "own" the planet, the Federation did. Even Picard, who was sympathetic to the Baku, stated that it was a Federation planet.
I can easily see the Federation setting the Baku up in some valley on another Federation planet, very similar to the one on the Federation planet they were removed from. Residing in that new valley would not entitle them to ownership of the whole planet upon which the new valley was located. That would be silly.