If done in the same way as BD/LH you would not be able to move anyone, either normal PAX or fellow GCH, you would simply have the choice of all seats that are available and should you chose to sit next to a free space it would be blocked for you unless the flight was too full to do so. You would still be free to choose a single seat further forward if you prefer but not at the expense of someone else's block.

Edited to say: So you are the one who causes the problem in the first place* When I choose an aisle seat next to a (non blocked!) free seat with the window seat occupied I always wonder why someone ends up plonking themselves in the middle seat when there are loads of free seats at the back. I also much prefer to be at the front but being boxed in between two randoms for any time at all is my worst nightmare, I'd rather sit at the back next to the loo than that!

*I joke of course, you should be free to plonk yourself wherever you like, even if it means being squashed next to a fat bugger like me