I saw where someone stored their Jeep hard top on the side of I-77 on the way home from work yesterday. Poor thing was smashed all over the place.
Like others mentioned, hooks or a ledge to sit them on, and build a simple frame around them and cover with siding that matches your house. Just make it wide enough for two people to stand beside the hardtop and lift it out. Have a roll up door on the outside of the structure to access the top.
Another idea would be a wood structure that is on casters, but structure locks in place on the side of the house. Structure holds the hard top, roll into place behind car, and flip hard top down and out and install on car. Roll structure back up to the side of the house empty and lock back into place. Have the exterior covered with matching house siding.
A few pics of hardtops and house and surrounding ground would be helpful to come up with ideas.