This idea is simple, but doesn't sound half bad, actually.

I allready have an array of all the tiles which are to be placed in the game. In stead of making another classlist point to the item allready in my array, I can just change a boolean (Placed := True) and change the X and Y coordinates.

It might become a bit tricky later on when I do have to do a recursive function on all the tiles, but this may suffice, that or I'll just stick with the huge 2d array.