I understand how to support tiered cakes, but shaped cakes are throwing me for a loop.

I tried to go to the adult themed board, but it said it didn't exist.... So to keep it clean, I'm making a rocket ship and I want it to stand up. I have the pans to make it. It would stand at about a foot high. Would it need support? If so, what kind?

I use a modified cake mix which makes it denser and easier to work with. I was thinking about trying to ganache it and then use MMF. With the ganache, would I still be able to detail the fondant or would the ganache be too hard underneath?

Nice way to describe what you are after
Any cake taller than 4" needs support to hold up what is above it. So for every additional 4" there needs to be supports in the cake under it.
Then, for additional safety add one long dowel through ALL the layers. Sharpen an end to a point and use a hammer to get it in *straight*.
In fact for that tall, I suggest making a special board to which you put a PVC pipe in a flange - OR you could use a thick wood dowel screwed into the base board - so it is very secure then put cakes down that pipe.
Hope you understnad that

Thanks, I understand what you are getting at! I have a pan so that I have two sides of the ship, would the central wooden dowel still work if the center is where the seam runs down? I'm just worried about it splitting in half.

Will the ganache harden enough to hold this cake together around the dowel?

Thanks! Just want to bump this back up.