Mazes in cupboards are fine for creating separate pathways to objectives, the problem that you will run into will be all of the empty space on the floor. You are basically building a giant open box and any detail that you put into it is going to slowly eat away at your frame rate. In order to keep your frame rate under control, you would want to have an even balance between action taking place in the open room, and action inside the cabinets as if they are buildings or tunnels.
Once way to get around that would be to focus the objective gameplay more like rats in the walls. If you’ve ever seen a cartoon with mice, they always have a lot clever paths inside the walls to get around the house. Using ropes, electrical cords, water pipes, homemade ladders, “mouse-sized” furniture, you could design an elaborate network of paths on the inside with branching paths that will take you out onto the counter top for your “outdoor” areas.
For instance, You have to dynamite the backside of a cracked tile to open a hole and allow you access to the kitchen counter. Or blow a pipe inside the wall to drain the dishwater out of the sink so the attackers can gain access to an objective.
Treat the counter tops as if they were the tops of a cliff or a mountain. You can look out across the kitchen to see the other side, but you wouldn’t go over there and you would not have to worry about putting too much detail on it. It would mostly be done with texture maps.
Also if you are basing your paths inside the walls, you could use multiple branches that lead to higher or lower elevations in other rooms. Maybe one hole leads to the bathroom tub and you have to sink the toy submarine. Construct a bridge made out of tooth brushes to get from the toilet to the tub. Maybe one branch could be a broom closet. It would be a small enough space that you could have more action at floor level without resorting to using a huge empty environment. With a four room layout, you have a natural junction where 1 wall from each room meets and this could be a crossroads where you capture the flag. Maybe the attackers need to destroy a mouse trap in order to steal the cheese and take it back to base.
What I am getting at is if you want this to be a fun objective map, you have to contain the action a little more. Identify the main points of interest in a room (such as the kitchen sink or the stove) and limit your action in that room to those areas. Weave these highlights together with a multi-level network of paths inside the walls and you will have a unique and fun map.
if i get some ideas ill post them here ok? 
