Well, I hate to give this advice, but if it's going to be hot, use fondant. Thats the only "heat resistant" cake frosting that I know of.
I would suggest also, that if it's going to be hot or warm, or the cake is going to be exposed for a long time before consumption, that the cake should be made in tiers, and not stacked ones, but separate ones.
Separate cake tiers will allow you to store them in a large freezer or fridge until ready to stack together on the stand or table. Which is also the other part of the advice........keeping them cold or frozen until they are to be placed out on the table or stand.
This one woman ordered a 8 tier STACKED wedding cake once, during the middle of the hot Texas summer. I mean, REALLY hot........102 degrees in the shade during the day.
I specifically told this woman that the cake must be picked up or delivered at night, because even though the trip was only about 5-10 minutes from the bakery, the buttercream that she wanted on the cake would be melted before it got to the building, during the daytime hours. She refused. I told her I would not be responsible, that she had been advised what would happen.
Even though I had this cake in the freezer overnight, it would still thaw out too fast in that kind of heat.
One of the bakers loaded the cake into the van and took it to the building it was supposed to be delivered to. He said he got it there ok, and got it in the building ok.........but as he sat it down on the table, it just went WHOOOOSH, and the stacks just slid off each other.
He had come back for a "repair" kit when that happened, and sped back to try to salvage the cake, as the stupid woman was apparently having conniption fits over this cake sliding across the table.
Stupid woman......I warned her what would happen.
LMAO
Sorry...........your requests reminded me of that.
So yeah, best advice I can give you........make the cake in separate tiers, and then either freeze them or put them in the fridge until time to put together for display.
As for the frosting itself, well.........like I said, fondant is the only heat resistant one I can think of.
Unless you are adept at working with hard chocolate coatings, fondant would be the one to go with, simply because it doesn't need to be frozen like buttercream or whipped frosting would be.
I would say, once you have your specifics all made certain, then ask this on here again. I know I can better help with more specifics of what you have to work with and what is wanted.
